16991531 has 2 divisors, whose sum is σ = 16991532. Its totient is φ = 16991530.

The previous prime is 16991509. The next prime is 16991537. The reversal of 16991531 is 13519961.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 16991531 - 2⁶ = 16991467 is a prime.

It is a super-2 number, since 2×16991531² = 577424251447922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 16991491 and 16991500.

It is not a weakly prime, because it can be changed into another prime (16991537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8495765 + 8495766.

It is an arithmetic number, because the mean of its divisors is an integer number (8495766).

Almost surely, 2^16991531 is an apocalyptic number.

16991531 is a deficient number, since it is larger than the sum of its proper divisors (1).

16991531 is an equidigital number, since it uses as much as digits as its factorization.

16991531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7290, while the sum is 35.

The square root of 16991531 is about 4122.0784805726. The cubic root of 16991531 is about 257.0854535738.

The spelling of 16991531 in words is "sixteen million, nine hundred ninety-one thousand, five hundred thirty-one".