21687637020 has 192 divisors, whose sum is σ = 76229959680. Its totient is φ = 4492046592.

The previous prime is 21687636961. The next prime is 21687637021. The reversal of 21687637020 is 2073678612.

It is a super-2 number, since 2×21687637020² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21687637021) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 124459 + ... + 242621.

It is an arithmetic number, because the mean of its divisors is an integer number (397031040).

Almost surely, 2^21687637020 is an apocalyptic number.

21687637020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21687637020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38114979840).

21687637020 is an abundant number, since it is smaller than the sum of its proper divisors (54542322660).

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

21687637020 is a wasteful number, since it uses less digits than its factorization.

21687637020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118224 (or 118222 counting only the distinct ones).

The product of its (nonzero) digits is 169344, while the sum is 42.

The spelling of 21687637020 in words is "twenty-one billion, six hundred eighty-seven million, six hundred thirty-seven thousand, twenty".