21663885 has 16 divisors (see below), whose sum is σ = 35781120. Its totient is φ = 11181120.

The previous prime is 21663881. The next prime is 21663911. The reversal of 21663885 is 58836612.

It is a happy number.

It is not a de Polignac number, because 21663885 - 2² = 21663881 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663881) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22830 + ... + 23759.

It is an arithmetic number, because the mean of its divisors is an integer number (2236320).

Almost surely, 2^21663885 is an apocalyptic number.

It is an amenable number.

21663885 is a deficient number, since it is larger than the sum of its proper divisors (14117235).

21663885 is a wasteful number, since it uses less digits than its factorization.

21663885 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46628.

The product of its digits is 69120, while the sum is 39.

The square root of 21663885 is about 4654.4478727342. The cubic root of 21663885 is about 278.7696226475.

The spelling of 21663885 in words is "twenty-one million, six hundred sixty-three thousand, eight hundred eighty-five".