21890866 has 8 divisors (see below), whose sum is σ = 34767900. Its totient is φ = 10301568.

The previous prime is 21890839. The next prime is 21890879. The reversal of 21890866 is 66809812.

It can be written as a sum of positive squares in 2 ways, for example, as 21669025 + 221841 = 4655^2 + 471^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 321891 + ... + 321958.

Almost surely, 2^21890866 is an apocalyptic number.

21890866 is a deficient number, since it is larger than the sum of its proper divisors (12877034).

21890866 is a wasteful number, since it uses less digits than its factorization.

21890866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 643868.

The product of its (nonzero) digits is 41472, while the sum is 40.

The square root of 21890866 is about 4678.7675727696. The cubic root of 21890866 is about 279.7398348701.

The spelling of 21890866 in words is "twenty-one million, eight hundred ninety thousand, eight hundred sixty-six".