1261538520 has 64 divisors (see below), whose sum is σ = 4128675840. Its totient is φ = 305827200.

The previous prime is 1261538513. The next prime is 1261538617. The reversal of 1261538520 is 258351621.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 476536 + ... + 479175.

It is an arithmetic number, because the mean of its divisors is an integer number (64510560).

Almost surely, 2^1261538520 is an apocalyptic number.

1261538520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1261538520 is an abundant number, since it is smaller than the sum of its proper divisors (2867137320).

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

1261538520 is a wasteful number, since it uses less digits than its factorization.

1261538520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 955736 (or 955732 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 33.

The square root of 1261538520 is about 35518.1435325666. The cubic root of 1261538520 is about 1080.5217300876.

The spelling of 1261538520 in words is "one billion, two hundred sixty-one million, five hundred thirty-eight thousand, five hundred twenty".