21309388 has 6 divisors (see below), whose sum is σ = 37291436. Its totient is φ = 10654692.

The previous prime is 21309383. The next prime is 21309397. The reversal of 21309388 is 88390312.

It is not an unprimeable number, because it can be changed into a prime (21309383) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2663670 + ... + 2663677.

Almost surely, 2^21309388 is an apocalyptic number.

It is an amenable number.

21309388 is a deficient number, since it is larger than the sum of its proper divisors (15982048).

21309388 is a wasteful number, since it uses less digits than its factorization.

21309388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5327351 (or 5327349 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 34.

The square root of 21309388 is about 4616.2092673535. The cubic root of 21309388 is about 277.2407035992.

The spelling of 21309388 in words is "twenty-one million, three hundred nine thousand, three hundred eighty-eight".