21389768 has 8 divisors (see below), whose sum is σ = 40105830. Its totient is φ = 10694880.

The previous prime is 21389743. The next prime is 21389773. The reversal of 21389768 is 86798312.

It can be written as a sum of positive squares in only one way, i.e., 14303524 + 7086244 = 3782^2 + 2662^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1336853 + ... + 1336868.

Almost surely, 2^21389768 is an apocalyptic number.

It is an amenable number.

21389768 is a deficient number, since it is larger than the sum of its proper divisors (18716062).

21389768 is a wasteful number, since it uses less digits than its factorization.

21389768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2673727 (or 2673723 counting only the distinct ones).

The product of its digits is 145152, while the sum is 44.

The square root of 21389768 is about 4624.9073504234. The cubic root of 21389768 is about 277.5888544831.

The spelling of 21389768 in words is "twenty-one million, three hundred eighty-nine thousand, seven hundred sixty-eight".