21561363540 has 96 divisors (see below), whose sum is σ = 68345544960. Its totient is φ = 5641204608.

The previous prime is 21561363539. The next prime is 21561363541. The reversal of 21561363540 is 4536316512.

21561363540 is a `hidden beast` number, since 2 + 1 + 5 + 6 + 13 + 635 + 4 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21561363539) and next prime (21561363541).

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 = 21561363495 and 21561363504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561363541) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 348064 + ... + 405303.

It is an arithmetic number, because the mean of its divisors is an integer number (711932760).

Almost surely, 2^21561363540 is an apocalyptic number.

21561363540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21561363540 is an abundant number, since it is smaller than the sum of its proper divisors (46784181420).

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

21561363540 is a wasteful number, since it uses less digits than its factorization.

21561363540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 753438 (or 753430 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 36.

The spelling of 21561363540 in words is "twenty-one billion, five hundred sixty-one million, three hundred sixty-three thousand, five hundred forty".