161991667 has 2 divisors, whose sum is σ = 161991668. Its totient is φ = 161991666.

The previous prime is 161991637. The next prime is 161991671. The reversal of 161991667 is 766199161.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161991667 is a prime.

It is not a weakly prime, because it can be changed into another prime (161991607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80995833 + 80995834.

It is an arithmetic number, because the mean of its divisors is an integer number (80995834).

Almost surely, 2^161991667 is an apocalyptic number.

161991667 is a deficient number, since it is larger than the sum of its proper divisors (1).

161991667 is an equidigital number, since it uses as much as digits as its factorization.

161991667 is an evil number, because the sum of its binary digits is even.

The product of its digits is 122472, while the sum is 46.

The square root of 161991667 is about 12727.5947059922. The cubic root of 161991667 is about 545.1268307351.

The spelling of 161991667 in words is "one hundred sixty-one million, nine hundred ninety-one thousand, six hundred sixty-seven".