21684766 has 16 divisors (see below), whose sum is σ = 33364800. Its totient is φ = 10565280.

The previous prime is 21684763. The next prime is 21684781. The reversal of 21684766 is 66748612.

21684766 = 54² + 55² + ... + 402².

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684763) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32476 + ... + 33136.

It is an arithmetic number, because the mean of its divisors is an integer number (2085300).

Almost surely, 2^21684766 is an apocalyptic number.

21684766 is a deficient number, since it is larger than the sum of its proper divisors (11680034).

21684766 is a wasteful number, since it uses less digits than its factorization.

21684766 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1059.

The product of its digits is 96768, while the sum is 40.

The square root of 21684766 is about 4656.6904556777. The cubic root of 21684766 is about 278.8591590546.

The spelling of 21684766 in words is "twenty-one million, six hundred eighty-four thousand, seven hundred sixty-six".