161491801 has 2 divisors, whose sum is σ = 161491802. Its totient is φ = 161491800.

The previous prime is 161491787. The next prime is 161491817. The reversal of 161491801 is 108194161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 161315401 + 176400 = 12701^2 + 420^2 .

It is an emirp because it is prime and its reverse (108194161) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 161491801 - 2⁵ = 161491769 is a prime.

It is not a weakly prime, because it can be changed into another prime (161491871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80745900 + 80745901.

It is an arithmetic number, because the mean of its divisors is an integer number (80745901).

Almost surely, 2^161491801 is an apocalyptic number.

It is an amenable number.

161491801 is a deficient number, since it is larger than the sum of its proper divisors (1).

161491801 is an equidigital number, since it uses as much as digits as its factorization.

161491801 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 31.

The square root of 161491801 is about 12707.9424377041. The cubic root of 161491801 is about 544.5655443964.

The spelling of 161491801 in words is "one hundred sixty-one million, four hundred ninety-one thousand, eight hundred one".