20561287213440 has 768 divisors, whose sum is σ = 76268135623680. Its totient is φ = 5091740172288.

The previous prime is 20561287213433. The next prime is 20561287213469. The reversal of 20561287213440 is 4431278216502.

20561287213440 is a `hidden beast` number, since 2 + 0 + 5 + 6 + 1 + 287 + 21 + 344 + 0 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 951328074 + ... + 951349686.

It is an arithmetic number, because the mean of its divisors is an integer number (99307468260).

Almost surely, 2^{20561287213440} is an apocalyptic number.

20561287213440 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 20561287213440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38134067811840).

20561287213440 is an abundant number, since it is smaller than the sum of its proper divisors (55706848410240).

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

20561287213440 is a wasteful number, since it uses less digits than its factorization.

20561287213440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21871 (or 21856 counting only the distinct ones).

The product of its (nonzero) digits is 645120, while the sum is 45.

The spelling of 20561287213440 in words is "twenty trillion, five hundred sixty-one billion, two hundred eighty-seven million, two hundred thirteen thousand, four hundred forty".