21977388 has 72 divisors (see below), whose sum is σ = 58705920. Its totient is φ = 6922080.

The previous prime is 21977383. The next prime is 21977399. The reversal of 21977388 is 88377912.

It is a super-3 number, since 3×21977388³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21977381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 52243 + ... + 52661.

It is an arithmetic number, because the mean of its divisors is an integer number (815360).

Almost surely, 2^21977388 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21977388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29352960).

21977388 is an abundant number, since it is smaller than the sum of its proper divisors (36728532).

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

21977388 is a wasteful number, since it uses less digits than its factorization.

21977388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 507 (or 502 counting only the distinct ones).

The product of its digits is 169344, while the sum is 45.

The square root of 21977388 is about 4688.0046928304. The cubic root of 21977388 is about 280.1079005910.

The spelling of 21977388 in words is "twenty-one million, nine hundred seventy-seven thousand, three hundred eighty-eight".