21666190 has 64 divisors (see below), whose sum is σ = 49714560. Its totient is φ = 6612480.

The previous prime is 21666167. The next prime is 21666191. The reversal of 21666190 is 9166612.

It is a super-2 number, since 2×21666190² = 938847578232200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666191) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 25980 + ... + 26800.

It is an arithmetic number, because the mean of its divisors is an integer number (776790).

Almost surely, 2^21666190 is an apocalyptic number.

21666190 is an abundant number, since it is smaller than the sum of its proper divisors (28048370).

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

21666190 is a wasteful number, since it uses less digits than its factorization.

21666190 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 877.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 21666190 is about 4654.6954787612. The cubic root of 21666190 is about 278.7795091659.

The spelling of 21666190 in words is "twenty-one million, six hundred sixty-six thousand, one hundred ninety".