21188889864 has 24 divisors (see below), whose sum is σ = 57386576910. Its totient is φ = 7062963264.

The previous prime is 21188889859. The next prime is 21188889871. The reversal of 21188889864 is 46898888112.

It can be written as a sum of positive squares in only one way, i.e., 20294281764 + 894608100 = 142458^2 + 29910^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 147144997 + ... + 147145140.

Almost surely, 2^21188889864 is an apocalyptic number.

21188889864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21188889864 is an abundant number, since it is smaller than the sum of its proper divisors (36197687046).

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

21188889864 is a wasteful number, since it uses less digits than its factorization.

21188889864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 294290149 (or 294290142 counting only the distinct ones).

The product of its digits is 14155776, while the sum is 63.

The spelling of 21188889864 in words is "twenty-one billion, one hundred eighty-eight million, eight hundred eighty-nine thousand, eight hundred sixty-four".