21123718 has 32 divisors (see below), whose sum is σ = 40066560. Its totient is φ = 8112960.

The previous prime is 21123709. The next prime is 21123721. The reversal of 21123718 is 81732112.

It is a happy number.

It is a super-2 number, since 2×21123718² = 892422924287048, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21123692 and 21123701.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10303 + ... + 12181.

It is an arithmetic number, because the mean of its divisors is an integer number (1252080).

Almost surely, 2^21123718 is an apocalyptic number.

21123718 is a deficient number, since it is larger than the sum of its proper divisors (18942842).

21123718 is a wasteful number, since it uses less digits than its factorization.

21123718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1972.

The product of its digits is 672, while the sum is 25.

The square root of 21123718 is about 4596.0546123822. The cubic root of 21123718 is about 276.4331485477.

The spelling of 21123718 in words is "twenty-one million, one hundred twenty-three thousand, seven hundred eighteen".