21665694 has 8 divisors (see below), whose sum is σ = 43331400. Its totient is φ = 7221896.

The previous prime is 21665689. The next prime is 21665713. The reversal of 21665694 is 49656612.

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

21665694 is an admirable number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1805469 + ... + 1805480.

It is an arithmetic number, because the mean of its divisors is an integer number (5416425).

Almost surely, 2^21665694 is an apocalyptic number.

21665694 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21665694 is a wasteful number, since it uses less digits than its factorization.

21665694 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3610954.

The product of its digits is 77760, while the sum is 39.

The square root of 21665694 is about 4654.6421989236. The cubic root of 21665694 is about 278.7773818008. Note that the first 3 decimals are identical.

The spelling of 21665694 in words is "twenty-one million, six hundred sixty-five thousand, six hundred ninety-four".