21988740 has 24 divisors (see below), whose sum is σ = 61568640. Its totient is φ = 5863648.

The previous prime is 21988739. The next prime is 21988741. The reversal of 21988740 is 4788912.

It is an interprime number because it is at equal distance from previous prime (21988739) and next prime (21988741).

It is not an unprimeable number, because it can be changed into a prime (21988741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 183180 + ... + 183299.

It is an arithmetic number, because the mean of its divisors is an integer number (2565360).

Almost surely, 2^21988740 is an apocalyptic number.

21988740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21988740 is an abundant number, since it is smaller than the sum of its proper divisors (39579900).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21988740 is a wasteful number, since it uses less digits than its factorization.

21988740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 366491 (or 366489 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 21988740 is about 4689.2152861646. The cubic root of 21988740 is about 280.1561204183.

The spelling of 21988740 in words is "twenty-one million, nine hundred eighty-eight thousand, seven hundred forty".