31471991 has 2 divisors, whose sum is σ = 31471992. Its totient is φ = 31471990.

The previous prime is 31471967. The next prime is 31472003. The reversal of 31471991 is 19917413.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31471991 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31471901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15735995 + 15735996.

It is an arithmetic number, because the mean of its divisors is an integer number (15735996).

Almost surely, 2^31471991 is an apocalyptic number.

31471991 is a deficient number, since it is larger than the sum of its proper divisors (1).

31471991 is an equidigital number, since it uses as much as digits as its factorization.

31471991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6804, while the sum is 35.

The square root of 31471991 is about 5609.9902851966. The cubic root of 31471991 is about 315.7243463495.

The spelling of 31471991 in words is "thirty-one million, four hundred seventy-one thousand, nine hundred ninety-one".