25221618 has 20 divisors (see below), whose sum is σ = 56515470. Its totient is φ = 8407152.

The previous prime is 25221617. The next prime is 25221653. The reversal of 25221618 is 81612252.

It is a happy number.

25221618 is a `hidden beast` number, since 25 + 2 + 21 + 618 = 666.

It can be written as a sum of positive squares in only one way, i.e., 15468489 + 9753129 = 3933^2 + 3123^2 .

It is a super-2 number, since 2×25221618² = 1272260029075848, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 25221591 and 25221600.

It is not an unprimeable number, because it can be changed into a prime (25221611) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 77683 + ... + 78006.

Almost surely, 2^25221618 is an apocalyptic number.

25221618 is an abundant number, since it is smaller than the sum of its proper divisors (31293852).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

25221618 is a wasteful number, since it uses less digits than its factorization.

25221618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155703 (or 155694 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 25221618 is about 5022.1129019567. The cubic root of 25221618 is about 293.2632531736.

The spelling of 25221618 in words is "twenty-five million, two hundred twenty-one thousand, six hundred eighteen".