21356644 has 24 divisors (see below), whose sum is σ = 39916800. Its totient is φ = 9975840.

The previous prime is 21356633. The next prime is 21356653. The reversal of 21356644 is 44665312.

It is a super-2 number, since 2×21356644² = 912212485885472, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (31).

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, 627 + ... + 6565.

It is an arithmetic number, because the mean of its divisors is an integer number (1663200).

Almost surely, 2^21356644 is an apocalyptic number.

It is an amenable number.

21356644 is a deficient number, since it is larger than the sum of its proper divisors (18560156).

21356644 is a wasteful number, since it uses less digits than its factorization.

21356644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6003 (or 6001 counting only the distinct ones).

The product of its digits is 17280, while the sum is 31.

The square root of 21356644 is about 4621.3249182458. The cubic root of 21356644 is about 277.4454899289.

The spelling of 21356644 in words is "twenty-one million, three hundred fifty-six thousand, six hundred forty-four".