21523618 has 16 divisors (see below), whose sum is σ = 34629120. Its totient is φ = 10002096.

The previous prime is 21523609. The next prime is 21523631. The reversal of 21523618 is 81632512.

It is a super-2 number, since 2×21523618² = 926532263619848, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3330 + ... + 7357.

It is an arithmetic number, because the mean of its divisors is an integer number (2164320).

Almost surely, 2^21523618 is an apocalyptic number.

21523618 is a deficient number, since it is larger than the sum of its proper divisors (13105502).

21523618 is a wasteful number, since it uses less digits than its factorization.

21523618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10761.

The product of its digits is 2880, while the sum is 28.

The square root of 21523618 is about 4639.3553431484. The cubic root of 21523618 is about 278.1666702367.

The spelling of 21523618 in words is "twenty-one million, five hundred twenty-three thousand, six hundred eighteen".