1631661391 has 2 divisors, whose sum is σ = 1631661392. Its totient is φ = 1631661390.

The previous prime is 1631661349. The next prime is 1631661397. The reversal of 1631661391 is 1931661361.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1631661391 - 2²⁵ = 1598106959 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1631661391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1631661397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 815830695 + 815830696.

It is an arithmetic number, because the mean of its divisors is an integer number (815830696).

Almost surely, 2^1631661391 is an apocalyptic number.

1631661391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1631661391 is an equidigital number, since it uses as much as digits as its factorization.

1631661391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17496, while the sum is 37.

The square root of 1631661391 is about 40393.8286251749. The cubic root of 1631661391 is about 1177.2716316123.

The spelling of 1631661391 in words is "one billion, six hundred thirty-one million, six hundred sixty-one thousand, three hundred ninety-one".