21621356 has 12 divisors (see below), whose sum is σ = 39142320. Its totient is φ = 10437840.

The previous prime is 21621337. The next prime is 21621371. The reversal of 21621356 is 65312612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 93080 + ... + 93311.

It is an arithmetic number, because the mean of its divisors is an integer number (3261860).

Almost surely, 2^21621356 is an apocalyptic number.

It is an amenable number.

21621356 is a deficient number, since it is larger than the sum of its proper divisors (17520964).

21621356 is a wasteful number, since it uses less digits than its factorization.

21621356 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186424 (or 186422 counting only the distinct ones).

The product of its digits is 2160, while the sum is 26.

The square root of 21621356 is about 4649.8769876202. The cubic root of 21621356 is about 278.5870829060.

Adding to 21621356 its reverse (65312612), we get a palindrome (86933968).

The spelling of 21621356 in words is "twenty-one million, six hundred twenty-one thousand, three hundred fifty-six".