1321561520 has 20 divisors (see below), whose sum is σ = 3072630720. Its totient is φ = 528624576.

The previous prime is 1321561499. The next prime is 1321561529. The reversal of 1321561520 is 251651231.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×1321561520² = 3493049702289420800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1321561520.

It is not an unprimeable number, because it can be changed into a prime (1321561529) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8259680 + ... + 8259839.

It is an arithmetic number, because the mean of its divisors is an integer number (153631536).

Almost surely, 2^1321561520 is an apocalyptic number.

1321561520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1321561520 is an abundant number, since it is smaller than the sum of its proper divisors (1751069200).

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

1321561520 is a wasteful number, since it uses less digits than its factorization.

1321561520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16519532 (or 16519526 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 1321561520 is about 36353.2876092383. The cubic root of 1321561520 is about 1097.3936973608.

The spelling of 1321561520 in words is "one billion, three hundred twenty-one million, five hundred sixty-one thousand, five hundred twenty".