21238664 has 8 divisors (see below), whose sum is σ = 39822510. Its totient is φ = 10619328.

The previous prime is 21238639. The next prime is 21238667. The reversal of 21238664 is 46683212.

It can be written as a sum of positive squares in only one way, i.e., 14002564 + 7236100 = 3742^2 + 2690^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21238664.

It is not an unprimeable number, because it can be changed into a prime (21238667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1327409 + ... + 1327424.

Almost surely, 2^21238664 is an apocalyptic number.

It is an amenable number.

21238664 is a deficient number, since it is larger than the sum of its proper divisors (18583846).

21238664 is a wasteful number, since it uses less digits than its factorization.

21238664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2654839 (or 2654835 counting only the distinct ones).

The product of its digits is 13824, while the sum is 32.

The square root of 21238664 is about 4608.5425027876. The cubic root of 21238664 is about 276.9336510840.

The spelling of 21238664 in words is "twenty-one million, two hundred thirty-eight thousand, six hundred sixty-four".