21108788 has 6 divisors (see below), whose sum is σ = 36940386. Its totient is φ = 10554392.

The previous prime is 21108757. The next prime is 21108793. The reversal of 21108788 is 88780112.

It can be written as a sum of positive squares in only one way, i.e., 17875984 + 3232804 = 4228^2 + 1798^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2638595 + ... + 2638602.

It is an arithmetic number, because the mean of its divisors is an integer number (6156731).

Almost surely, 2^21108788 is an apocalyptic number.

It is an amenable number.

21108788 is a deficient number, since it is larger than the sum of its proper divisors (15831598).

21108788 is a wasteful number, since it uses less digits than its factorization.

21108788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5277201 (or 5277199 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 35.

The square root of 21108788 is about 4594.4301061176. The cubic root of 21108788 is about 276.3680066121.

Subtracting from 21108788 its sum of digits (35), we obtain a triangular number (21108753 = T₆₄₉₇).

The spelling of 21108788 in words is "twenty-one million, one hundred eight thousand, seven hundred eighty-eight".