31520561 has 4 divisors (see below), whose sum is σ = 31539312. Its totient is φ = 31501812.

The previous prime is 31520537. The next prime is 31520569. The reversal of 31520561 is 16502513.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 31520561 - 2⁶ = 31520497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31520569) 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, 6575 + ... + 10308.

It is an arithmetic number, because the mean of its divisors is an integer number (7884828).

Almost surely, 2^31520561 is an apocalyptic number.

It is an amenable number.

31520561 is a deficient number, since it is larger than the sum of its proper divisors (18751).

31520561 is a wasteful number, since it uses less digits than its factorization.

31520561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18750.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 31520561 is about 5614.3175008188. The cubic root of 31520561 is about 315.8866795776.

The spelling of 31520561 in words is "thirty-one million, five hundred twenty thousand, five hundred sixty-one".