21005788 has 12 divisors (see below), whose sum is σ = 37753912. Its totient is φ = 10218960.

The previous prime is 21005779. The next prime is 21005791. The reversal of 21005788 is 88750012.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70818 + ... + 71113.

Almost surely, 2^21005788 is an apocalyptic number.

It is an amenable number.

21005788 is a deficient number, since it is larger than the sum of its proper divisors (16748124).

21005788 is a wasteful number, since it uses less digits than its factorization.

21005788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141972 (or 141970 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 31.

The square root of 21005788 is about 4583.2071740213. The cubic root of 21005788 is about 275.9177623782.

The spelling of 21005788 in words is "twenty-one million, five thousand, seven hundred eighty-eight".