21613866 has 16 divisors (see below), whose sum is σ = 43395264. Its totient is φ = 7176704.

The previous prime is 21613841. The next prime is 21613873. The reversal of 21613866 is 66831612.

It is a plaindrome in base 11.

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, 5271 + ... + 8426.

It is an arithmetic number, because the mean of its divisors is an integer number (2712204).

Almost surely, 2^21613866 is an apocalyptic number.

21613866 is an abundant number, since it is smaller than the sum of its proper divisors (21781398).

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

21613866 is a wasteful number, since it uses less digits than its factorization.

21613866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13965.

The product of its digits is 10368, while the sum is 33.

The square root of 21613866 is about 4649.0715202070. The cubic root of 21613866 is about 278.5549101129.

The spelling of 21613866 in words is "twenty-one million, six hundred thirteen thousand, eight hundred sixty-six".