21540388 has 12 divisors (see below), whose sum is σ = 38995740. Its totient is φ = 10398752.

The previous prime is 21540383. The next prime is 21540437. The reversal of 21540388 is 88304512.

It can be written as a sum of positive squares in 2 ways, for example, as 16305444 + 5234944 = 4038^2 + 2288^2 .

It is not an unprimeable number, because it can be changed into a prime (21540383) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 92731 + ... + 92962.

It is an arithmetic number, because the mean of its divisors is an integer number (3249645).

Almost surely, 2^21540388 is an apocalyptic number.

It is an amenable number.

21540388 is a deficient number, since it is larger than the sum of its proper divisors (17455352).

21540388 is a wasteful number, since it uses less digits than its factorization.

21540388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185726 (or 185724 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 31.

The square root of 21540388 is about 4641.1623544108. The cubic root of 21540388 is about 278.2388954554.

The spelling of 21540388 in words is "twenty-one million, five hundred forty thousand, three hundred eighty-eight".