25721865 has 24 divisors (see below), whose sum is σ = 48015240. Its totient is φ = 12662784.

The previous prime is 25721849. The next prime is 25721923. The reversal of 25721865 is 56812752.

It is a happy number.

25721865 is a `hidden beast` number, since 2 + 572 + 1 + 86 + 5 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 1159929 + 24561936 = 1077^2 + 4956^2 .

It is not a de Polignac number, because 25721865 - 2⁴ = 25721849 is a prime.

It is a super-2 number, since 2×25721865² = 1323228678156450, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21400 + ... + 22569.

It is an arithmetic number, because the mean of its divisors is an integer number (2000635).

Almost surely, 2^25721865 is an apocalyptic number.

It is an amenable number.

25721865 is a deficient number, since it is larger than the sum of its proper divisors (22293375).

25721865 is a wasteful number, since it uses less digits than its factorization.

25721865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43993 (or 43990 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 25721865 is about 5071.6728009603. The cubic root of 25721865 is about 295.1894407068.

It can be divided in two parts, 257 and 21865, that added together give a palindrome (22122).

The spelling of 25721865 in words is "twenty-five million, seven hundred twenty-one thousand, eight hundred sixty-five".