21306872240640 has 2400 divisors, whose sum is σ = 94540826906064. Its totient is φ = 4557168967680.

The previous prime is 21306872240597. The next prime is 21306872240671. The reversal of 21306872240640 is 4604227860312.

It is a happy number.

21306872240640 is a `hidden beast` number, since 2 + 1 + 306 + 87 + 224 + 0 + 6 + 40 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 10528415541504 + 10778456699136 = 3244752^2 + 3283056^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 50610147630 + ... + 50610148050.

Almost surely, 2^{21306872240640} is an apocalyptic number.

21306872240640 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 21306872240640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47270413453032).

21306872240640 is an abundant number, since it is smaller than the sum of its proper divisors (73233954665424).

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

21306872240640 is a wasteful number, since it uses less digits than its factorization.

21306872240640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780 (or 748 counting only the distinct ones).

The product of its (nonzero) digits is 774144, while the sum is 45.

The spelling of 21306872240640 in words is "twenty-one trillion, three hundred six billion, eight hundred seventy-two million, two hundred forty thousand, six hundred forty".