2157561256644 has 240 divisors, whose sum is σ = 5925492308736. Its totient is φ = 686669011200.

The previous prime is 2157561256637. The next prime is 2157561256649. The reversal of 2157561256644 is 4466521657512.

2157561256644 is a `hidden beast` number, since 2 + 1 + 5 + 75 + 6 + 1 + 2 + 566 + 4 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (2157561256649) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 151709454 + ... + 151723674.

Almost surely, 2^{2157561256644} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2157561256644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2962746154368).

2157561256644 is an abundant number, since it is smaller than the sum of its proper divisors (3767931052092).

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

2157561256644 is an equidigital number, since it uses as much as digits as its factorization.

2157561256644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14340 (or 14314 counting only the distinct ones).

The product of its digits is 12096000, while the sum is 54.

The spelling of 2157561256644 in words is "two trillion, one hundred fifty-seven billion, five hundred sixty-one million, two hundred fifty-six thousand, six hundred forty-four".