5631991 has 2 divisors, whose sum is σ = 5631992. Its totient is φ = 5631990.

The previous prime is 5631979. The next prime is 5632001. The reversal of 5631991 is 1991365.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 5631991 - 2¹⁹ = 5107703 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (5631911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2815995 + 2815996.

It is an arithmetic number, because the mean of its divisors is an integer number (2815996).

Almost surely, 2^5631991 is an apocalyptic number.

5631991 is a deficient number, since it is larger than the sum of its proper divisors (1).

5631991 is an equidigital number, since it uses as much as digits as its factorization.

5631991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7290, while the sum is 34.

The square root of 5631991 is about 2373.1816196827. The cubic root of 5631991 is about 177.9183124736.

The spelling of 5631991 in words is "five million, six hundred thirty-one thousand, nine hundred ninety-one".