1261542040 has 128 divisors (see below), whose sum is σ = 3224862720. Its totient is φ = 440128000.

The previous prime is 1261542013. The next prime is 1261542049. The reversal of 1261542040 is 402451621.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 1261541996 and 1261542014.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261542049) 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, 1095465 + ... + 1096615.

It is an arithmetic number, because the mean of its divisors is an integer number (25194240).

Almost surely, 2^1261542040 is an apocalyptic number.

1261542040 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 1261542040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1612431360).

1261542040 is an abundant number, since it is smaller than the sum of its proper divisors (1963320680).

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

1261542040 is a wasteful number, since it uses less digits than its factorization.

1261542040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1273 (or 1269 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 1261542040 is about 35518.1930846714. The cubic root of 1261542040 is about 1080.5227350597.

Adding to 1261542040 its reverse (402451621), we get a palindrome (1663993661).

The spelling of 1261542040 in words is "one billion, two hundred sixty-one million, five hundred forty-two thousand, forty".