21640843392 has 128 divisors (see below), whose sum is σ = 65755760640. Its totient is φ = 6177420288.

The previous prime is 21640843387. The next prime is 21640843397. The reversal of 21640843392 is 29334804612.

It is an interprime number because it is at equal distance from previous prime (21640843387) and next prime (21640843397).

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×21640843392² (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 not an unprimeable number, because it can be changed into a prime (21640843397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3563943 + ... + 3570009.

It is an arithmetic number, because the mean of its divisors is an integer number (513716880).

Almost surely, 2^21640843392 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21640843392, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32877880320).

21640843392 is an abundant number, since it is smaller than the sum of its proper divisors (44114917248).

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

21640843392 is a wasteful number, since it uses less digits than its factorization.

21640843392 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7418 (or 7406 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 42.

The spelling of 21640843392 in words is "twenty-one billion, six hundred forty million, eight hundred forty-three thousand, three hundred ninety-two".