21317721264 has 240 divisors, whose sum is σ = 72064479840. Its totient is φ = 6090287616.

The previous prime is 21317721263. The next prime is 21317721277. The reversal of 21317721264 is 46212771312.

21317721264 is a `hidden beast` number, since 213 + 177 + 212 + 64 = 666.

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

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21317721263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1708392 + ... + 1720824.

It is an arithmetic number, because the mean of its divisors is an integer number (300268666).

Almost surely, 2^21317721264 is an apocalyptic number.

21317721264 is a gapful number since it is divisible by the number (24) 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 21317721264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36032239920).

21317721264 is an abundant number, since it is smaller than the sum of its proper divisors (50746758576).

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

21317721264 is an equidigital number, since it uses as much as digits as its factorization.

21317721264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12476 (or 12445 counting only the distinct ones).

The product of its digits is 28224, while the sum is 36.

The spelling of 21317721264 in words is "twenty-one billion, three hundred seventeen million, seven hundred twenty-one thousand, two hundred sixty-four".