21995388 has 84 divisors (see below), whose sum is σ = 60901960. Its totient is φ = 6928416.

The previous prime is 21995387. The next prime is 21995401. The reversal of 21995388 is 88359912.

It is a happy number.

21995388 is a `hidden beast` number, since 21 + 99 + 538 + 8 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21995387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 55206 + ... + 55602.

Almost surely, 2^21995388 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 21995388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30450980).

21995388 is an abundant number, since it is smaller than the sum of its proper divisors (38906572).

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

21995388 is a wasteful number, since it uses less digits than its factorization.

21995388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438 (or 421 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 21995388 is about 4689.9240932024. The cubic root of 21995388 is about 280.1843513859.

The spelling of 21995388 in words is "twenty-one million, nine hundred ninety-five thousand, three hundred eighty-eight".