2157731 has 2 divisors, whose sum is σ = 2157732. Its totient is φ = 2157730.

The previous prime is 2157721. The next prime is 2157733. The reversal of 2157731 is 1377512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 2157731 - 2⁶ = 2157667 is a prime.

It is a super-2 number, since 2×2157731² = 9311606136722, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 2157733, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2157731.

It is not a weakly prime, because it can be changed into another prime (2157733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1078865 + 1078866.

It is an arithmetic number, because the mean of its divisors is an integer number (1078866).

2^2157731 is an apocalyptic number.

2157731 is a deficient number, since it is larger than the sum of its proper divisors (1).

2157731 is an equidigital number, since it uses as much as digits as its factorization.

2157731 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1470, while the sum is 26.

The square root of 2157731 is about 1468.9217133666. The cubic root of 2157731 is about 129.2208024666.

The spelling of 2157731 in words is "two million, one hundred fifty-seven thousand, seven hundred thirty-one".