21172618 has 4 divisors (see below), whose sum is σ = 31758930. Its totient is φ = 10586308.

The previous prime is 21172601. The next prime is 21172637. The reversal of 21172618 is 81627112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20820969 + 351649 = 4563^2 + 593^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5293153 + ... + 5293156.

Almost surely, 2^21172618 is an apocalyptic number.

21172618 is a deficient number, since it is larger than the sum of its proper divisors (10586312).

21172618 is a wasteful number, since it uses less digits than its factorization.

21172618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10586311.

The product of its digits is 1344, while the sum is 28.

The square root of 21172618 is about 4601.3713173357. The cubic root of 21172618 is about 276.6462922691.

The spelling of 21172618 in words is "twenty-one million, one hundred seventy-two thousand, six hundred eighteen".