25631981 has 4 divisors (see below), whose sum is σ = 25653600. Its totient is φ = 25610364.

The previous prime is 25631941. The next prime is 25632041. The reversal of 25631981 is 18913652.

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 25631981 - 2¹⁸ = 25369837 is a prime.

It is a super-2 number, since 2×25631981² = 1313996899968722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25631941) 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, 8921 + ... + 11438.

It is an arithmetic number, because the mean of its divisors is an integer number (6413400).

Almost surely, 2^25631981 is an apocalyptic number.

It is an amenable number.

25631981 is a deficient number, since it is larger than the sum of its proper divisors (21619).

25631981 is a wasteful number, since it uses less digits than its factorization.

25631981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21618.

The product of its digits is 12960, while the sum is 35.

The square root of 25631981 is about 5062.8036699047. The cubic root of 25631981 is about 294.8451969571.

The spelling of 25631981 in words is "twenty-five million, six hundred thirty-one thousand, nine hundred eighty-one".