21860720640 has 560 divisors, whose sum is σ = 85637217600. Its totient is φ = 5290721280.

The previous prime is 21860720633. The next prime is 21860720641. The reversal of 21860720640 is 4602706812.

21860720640 is a `hidden beast` number, since 2 + 1 + 8 + 6 + 0 + 7 + 2 + 0 + 640 = 666.

It is a super-2 number, since 2×21860720640² (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 a junction number, because it is equal to n+sod(n) for n = 21860720595 and 21860720604.

It is not an unprimeable number, because it can be changed into a prime (21860720641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 36495061 + ... + 36495659.

Almost surely, 2^21860720640 is an apocalyptic number.

21860720640 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 21860720640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42818608800).

21860720640 is an abundant number, since it is smaller than the sum of its proper divisors (63776496960).

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

21860720640 is an equidigital number, since it uses as much as digits as its factorization.

21860720640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 653 (or 620 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The spelling of 21860720640 in words is "twenty-one billion, eight hundred sixty million, seven hundred twenty thousand, six hundred forty".