31172561 has 4 divisors (see below), whose sum is σ = 35625792. Its totient is φ = 26719332.

The previous prime is 31172551. The next prime is 31172573. The reversal of 31172561 is 16527113.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16527113 = 107 ⋅154459.

It is a cyclic number.

It is not a de Polignac number, because 31172561 - 2⁶ = 31172497 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 31172561.

It is not an unprimeable number, because it can be changed into a prime (31172551) 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, 2226605 + ... + 2226618.

It is an arithmetic number, because the mean of its divisors is an integer number (8906448).

Almost surely, 2^31172561 is an apocalyptic number.

It is an amenable number.

31172561 is a deficient number, since it is larger than the sum of its proper divisors (4453231).

31172561 is an equidigital number, since it uses as much as digits as its factorization.

31172561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4453230.

The product of its digits is 1260, while the sum is 26.

The square root of 31172561 is about 5583.2392927404. The cubic root of 31172561 is about 314.7198685291.

Adding to 31172561 its reverse (16527113), we get a palindrome (47699674).

The spelling of 31172561 in words is "thirty-one million, one hundred seventy-two thousand, five hundred sixty-one".