21100664 has 24 divisors (see below), whose sum is σ = 42843960. Its totient is φ = 9738144.

The previous prime is 21100657. The next prime is 21100687. The reversal of 21100664 is 46600112.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6452 + ... + 9155.

It is an arithmetic number, because the mean of its divisors is an integer number (1785165).

Almost surely, 2^21100664 is an apocalyptic number.

It is an amenable number.

21100664 is an abundant number, since it is smaller than the sum of its proper divisors (21743296).

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

21100664 is a wasteful number, since it uses less digits than its factorization.

21100664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15639 (or 15622 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21100664 is about 4593.5459070309. The cubic root of 21100664 is about 276.3325474189.

Adding to 21100664 its reverse (46600112), we get a palindrome (67700776).

The spelling of 21100664 in words is "twenty-one million, one hundred thousand, six hundred sixty-four".