21439618 has 8 divisors (see below), whose sum is σ = 34051212. Its totient is φ = 10089216.

The previous prime is 21439577. The next prime is 21439633. The reversal of 21439618 is 81693412.

It can be written as a sum of positive squares in 2 ways, for example, as 20223009 + 1216609 = 4497^2 + 1103^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Harshad number since it is a multiple of its sum of digits (34), and also a Moran number because the ratio is a prime number: 630577 = 21439618 / (2 + 1 + 4 + 3 + 9 + 6 + 1 + 8).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 315255 + ... + 315322.

Almost surely, 2^21439618 is an apocalyptic number.

21439618 is a deficient number, since it is larger than the sum of its proper divisors (12611594).

21439618 is a wasteful number, since it uses less digits than its factorization.

21439618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 630596.

The product of its digits is 10368, while the sum is 34.

The square root of 21439618 is about 4630.2935112150. The cubic root of 21439618 is about 277.8043324066.

The spelling of 21439618 in words is "twenty-one million, four hundred thirty-nine thousand, six hundred eighteen".