21002791680 has 432 divisors, whose sum is σ = 79617152160. Its totient is φ = 5080154112.

The previous prime is 21002791673. The next prime is 21002791687. The reversal of 21002791680 is 8619720012.

21002791680 = T₁₁₇₈₅ + T₁₁₇₈₆ + ... + T₁₂₀₇₉.

It is an interprime number because it is at equal distance from previous prime (21002791673) and next prime (21002791687).

It is a super-2 number, since 2×21002791680² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21002791687) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 8834652 + ... + 8837028.

Almost surely, 2^21002791680 is an apocalyptic number.

21002791680 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 21002791680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39808576080).

21002791680 is an abundant number, since it is smaller than the sum of its proper divisors (58614360480).

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

21002791680 is a wasteful number, since it uses less digits than its factorization.

21002791680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2476 (or 2459 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The spelling of 21002791680 in words is "twenty-one billion, two million, seven hundred ninety-one thousand, six hundred eighty".