21663894 has 32 divisors (see below), whose sum is σ = 50017536. Its totient is φ = 6127200.

The previous prime is 21663881. The next prime is 21663911. The reversal of 21663894 is 49836612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1689 + ... + 6795.

It is an arithmetic number, because the mean of its divisors is an integer number (1563048).

Almost surely, 2^21663894 is an apocalyptic number.

21663894 is an abundant number, since it is smaller than the sum of its proper divisors (28353642).

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

21663894 is a wasteful number, since it uses less digits than its factorization.

21663894 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5220.

The product of its digits is 62208, while the sum is 39.

The square root of 21663894 is about 4654.4488395513. The cubic root of 21663894 is about 278.7696612514.

The spelling of 21663894 in words is "twenty-one million, six hundred sixty-three thousand, eight hundred ninety-four".