21039988 has 6 divisors (see below), whose sum is σ = 36819986. Its totient is φ = 10519992.

The previous prime is 21039971. The next prime is 21039989. The reversal of 21039988 is 88993012.

It can be written as a sum of positive squares in only one way, i.e., 14424804 + 6615184 = 3798^2 + 2572^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21039988.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2629995 + ... + 2630002.

Almost surely, 2^21039988 is an apocalyptic number.

It is an amenable number.

21039988 is a deficient number, since it is larger than the sum of its proper divisors (15779998).

21039988 is a wasteful number, since it uses less digits than its factorization.

21039988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5260001 (or 5259999 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 21039988 is about 4586.9366684095. The cubic root of 21039988 is about 276.0674238414.

The spelling of 21039988 in words is "twenty-one million, thirty-nine thousand, nine hundred eighty-eight".