21391356 has 24 divisors (see below), whose sum is σ = 57043840. Its totient is φ = 6111792.

The previous prime is 21391343. The next prime is 21391361. The reversal of 21391356 is 65319312.

It is a super-2 number, since 2×21391356² = 915180223037472, which contains 22 as substring.

It is a congruent number.

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, 127246 + ... + 127413.

Almost surely, 2^21391356 is an apocalyptic number.

It is an amenable number.

21391356 is an abundant number, since it is smaller than the sum of its proper divisors (35652484).

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

21391356 is a wasteful number, since it uses less digits than its factorization.

21391356 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254673 (or 254671 counting only the distinct ones).

The product of its digits is 4860, while the sum is 30.

The square root of 21391356 is about 4625.0790263519. The cubic root of 21391356 is about 277.5957238141.

The spelling of 21391356 in words is "twenty-one million, three hundred ninety-one thousand, three hundred fifty-six".