31125561 has 4 divisors (see below), whose sum is σ = 41500752. Its totient is φ = 20750372.

The previous prime is 31125529. The next prime is 31125571. The reversal of 31125561 is 16552113.

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: 16552113 = 3 ⋅5517371.

It is a cyclic number.

It is not a de Polignac number, because 31125561 - 2⁵ = 31125529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31125571) 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, 5187591 + ... + 5187596.

It is an arithmetic number, because the mean of its divisors is an integer number (10375188).

Almost surely, 2^31125561 is an apocalyptic number.

It is an amenable number.

31125561 is a deficient number, since it is larger than the sum of its proper divisors (10375191).

31125561 is a wasteful number, since it uses less digits than its factorization.

31125561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10375190.

The product of its digits is 900, while the sum is 24.

The square root of 31125561 is about 5579.0286789010. The cubic root of 31125561 is about 314.5616174514.

Adding to 31125561 its reverse (16552113), we get a palindrome (47677674).

The spelling of 31125561 in words is "thirty-one million, one hundred twenty-five thousand, five hundred sixty-one".