1265660640 has 192 divisors, whose sum is σ = 4485741120. Its totient is φ = 337416192.

The previous prime is 1265660633. The next prime is 1265660647. The reversal of 1265660640 is 460665621.

It is a happy number.

1265660640 is a `hidden beast` number, since 1 + 2 + 6 + 5 + 6 + 6 + 0 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (1265660633) and next prime (1265660647).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 1265660595 and 1265660604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1265660647) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 348112 + ... + 351728.

It is an arithmetic number, because the mean of its divisors is an integer number (23363235).

Almost surely, 2^1265660640 is an apocalyptic number.

1265660640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1265660640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2242870560).

1265660640 is an abundant number, since it is smaller than the sum of its proper divisors (3220080480).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1265660640 is an frugal number, since it uses more digits than its factorization.

1265660640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3653 (or 3627 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The square root of 1265660640 is about 35576.1245781493. The cubic root of 1265660640 is about 1081.6973310722.

The spelling of 1265660640 in words is "one billion, two hundred sixty-five million, six hundred sixty thousand, six hundred forty".