21021686931840 has 2048 divisors, whose sum is σ = 87777180057600. Its totient is φ = 4163879043072.

The previous prime is 21021686931829. The next prime is 21021686931841. The reversal of 21021686931840 is 4813968612012.

It is a super-2 number, since 2×21021686931840² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021686931841) by changing a digit.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 40194429819 + ... + 40194430341.

It is an arithmetic number, because the mean of its divisors is an integer number (42859951200).

Almost surely, 2^{21021686931840} is an apocalyptic number.

21021686931840 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 21021686931840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43888590028800).

21021686931840 is an abundant number, since it is smaller than the sum of its proper divisors (66755493125760).

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

21021686931840 is a wasteful number, since it uses less digits than its factorization.

21021686931840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 832 (or 820 counting only the distinct ones).

The product of its (nonzero) digits is 995328, while the sum is 51.

The spelling of 21021686931840 in words is "twenty-one trillion, twenty-one billion, six hundred eighty-six million, nine hundred thirty-one thousand, eight hundred forty".