21637381788 has 72 divisors (see below), whose sum is σ = 63176546160. Its totient is φ = 6171087360.

The previous prime is 21637381757. The next prime is 21637381789. The reversal of 21637381788 is 88718373612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21637381789) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1600323 + ... + 1613786.

It is an arithmetic number, because the mean of its divisors is an integer number (877452030).

Almost surely, 2^21637381788 is an apocalyptic number.

It is an amenable number.

21637381788 is an abundant number, since it is smaller than the sum of its proper divisors (41539164372).

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

21637381788 is a wasteful number, since it uses less digits than its factorization.

21637381788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3214147 (or 3214142 counting only the distinct ones).

The product of its digits is 2709504, while the sum is 54.

The spelling of 21637381788 in words is "twenty-one billion, six hundred thirty-seven million, three hundred eighty-one thousand, seven hundred eighty-eight".