21288788 has 6 divisors (see below), whose sum is σ = 37255386. Its totient is φ = 10644392.

The previous prime is 21288779. The next prime is 21288829. The reversal of 21288788 is 88788212.

It can be written as a sum of positive squares in only one way, i.e., 20232004 + 1056784 = 4498^2 + 1028^2 .

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, 2661095 + ... + 2661102.

It is an arithmetic number, because the mean of its divisors is an integer number (6209231).

Almost surely, 2^21288788 is an apocalyptic number.

It is an amenable number.

21288788 is a deficient number, since it is larger than the sum of its proper divisors (15966598).

21288788 is a wasteful number, since it uses less digits than its factorization.

21288788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5322201 (or 5322199 counting only the distinct ones).

The product of its digits is 114688, while the sum is 44.

The square root of 21288788 is about 4613.9774598496. The cubic root of 21288788 is about 277.1513376692.

The spelling of 21288788 in words is "twenty-one million, two hundred eighty-eight thousand, seven hundred eighty-eight".