21981588 has 12 divisors (see below), whose sum is σ = 51290400. Its totient is φ = 7327192.

The previous prime is 21981587. The next prime is 21981593. The reversal of 21981588 is 88518912.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-2 number, since 2×21981588² = 966380422003488, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981587) 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 3 ways as a sum of consecutive naturals, for example, 915888 + ... + 915911.

It is an arithmetic number, because the mean of its divisors is an integer number (4274200).

Almost surely, 2^21981588 is an apocalyptic number.

It is an amenable number.

21981588 is an abundant number, since it is smaller than the sum of its proper divisors (29308812).

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

21981588 is a wasteful number, since it uses less digits than its factorization.

21981588 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1831806 (or 1831804 counting only the distinct ones).

The product of its digits is 46080, while the sum is 42.

The square root of 21981588 is about 4688.4526232010. The cubic root of 21981588 is about 280.1257428425.

The spelling of 21981588 in words is "twenty-one million, nine hundred eighty-one thousand, five hundred eighty-eight".