21663516 has 48 divisors (see below), whose sum is σ = 60286464. Its totient is φ = 5919936.

The previous prime is 21663511. The next prime is 21663527. The reversal of 21663516 is 61536612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663511) 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, 3675 + ... + 7538.

It is an arithmetic number, because the mean of its divisors is an integer number (1255968).

Almost surely, 2^21663516 is an apocalyptic number.

It is an amenable number.

21663516 is an abundant number, since it is smaller than the sum of its proper divisors (38622948).

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

21663516 is a wasteful number, since it uses less digits than its factorization.

21663516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11250 (or 11248 counting only the distinct ones).

The product of its digits is 6480, while the sum is 30.

The square root of 21663516 is about 4654.4082330625. The cubic root of 21663516 is about 278.7680398816.

The spelling of 21663516 in words is "twenty-one million, six hundred sixty-three thousand, five hundred sixteen".