2157381681 has 64 divisors (see below), whose sum is σ = 3721310208. Its totient is φ = 1081237248.

The previous prime is 2157381679. The next prime is 2157381689. The reversal of 2157381681 is 1861837512.

It is not a de Polignac number, because 2157381681 - 2¹ = 2157381679 is a prime.

It is a super-2 number, since 2×2157381681² = 9308591435028771522, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2157381689) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 431860 + ... + 436826.

It is an arithmetic number, because the mean of its divisors is an integer number (58145472).

Almost surely, 2^2157381681 is an apocalyptic number.

2157381681 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2157381681 is a deficient number, since it is larger than the sum of its proper divisors (1563928527).

2157381681 is a wasteful number, since it uses less digits than its factorization.

2157381681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5070.

The product of its digits is 80640, while the sum is 42.

The square root of 2157381681 is about 46447.6229854661. The cubic root of 2157381681 is about 1292.1382882664.

The spelling of 2157381681 in words is "two billion, one hundred fifty-seven million, three hundred eighty-one thousand, six hundred eighty-one".