1265509440 has 448 divisors, whose sum is σ = 5069433600. Its totient is φ = 294617088.

The previous prime is 1265509439. The next prime is 1265509457. The reversal of 1265509440 is 449055621.

1265509440 is a `hidden beast` number, since 12 + 6 + 550 + 94 + 4 + 0 = 666.

It is a super-2 number, since 2×1265509440² = 3203028285458227200, which contains 22 as substring.

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 = 1265509395 and 1265509404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2133784 + ... + 2134376.

It is an arithmetic number, because the mean of its divisors is an integer number (11315700).

Almost surely, 2^1265509440 is an apocalyptic number.

1265509440 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 1265509440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2534716800).

1265509440 is an abundant number, since it is smaller than the sum of its proper divisors (3803924160).

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

1265509440 is a wasteful number, since it uses less digits than its factorization.

1265509440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 651 (or 635 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The square root of 1265509440 is about 35573.9994940125. Note that the first 3 decimals coincide. The cubic root of 1265509440 is about 1081.6542549783.

Adding to 1265509440 its sum of digits (36), we get a square (1265509476 = 35574²).

The spelling of 1265509440 in words is "one billion, two hundred sixty-five million, five hundred nine thousand, four hundred forty".