21318672640 has 72 divisors (see below), whose sum is σ = 51113801088. Its totient is φ = 8519301120.

The previous prime is 21318672637. The next prime is 21318672643. The reversal of 21318672640 is 4627681312.

It is an interprime number because it is at equal distance from previous prime (21318672637) and next prime (21318672643).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 21318672593 and 21318672602.

It is not an unprimeable number, because it can be changed into a prime (21318672643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1430025 + ... + 1444855.

It is an arithmetic number, because the mean of its divisors is an integer number (709913904).

Almost surely, 2^21318672640 is an apocalyptic number.

21318672640 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 21318672640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25556900544).

21318672640 is an abundant number, since it is smaller than the sum of its proper divisors (29795128448).

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

21318672640 is a wasteful number, since it uses less digits than its factorization.

21318672640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15975 (or 15961 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 40.

The spelling of 21318672640 in words is "twenty-one billion, three hundred eighteen million, six hundred seventy-two thousand, six hundred forty".