165661901 has 2 divisors, whose sum is σ = 165661902. Its totient is φ = 165661900.

The previous prime is 165661897. The next prime is 165661961. The reversal of 165661901 is 109166561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 164506276 + 1155625 = 12826^2 + 1075^2 .

It is a cyclic number.

It is not a de Polignac number, because 165661901 - 2² = 165661897 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165661961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82830950 + 82830951.

It is an arithmetic number, because the mean of its divisors is an integer number (82830951).

Almost surely, 2^165661901 is an apocalyptic number.

It is an amenable number.

165661901 is a deficient number, since it is larger than the sum of its proper divisors (1).

165661901 is an equidigital number, since it uses as much as digits as its factorization.

165661901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9720, while the sum is 35.

The square root of 165661901 is about 12870.9712531728. The cubic root of 165661901 is about 549.2130906489.

The spelling of 165661901 in words is "one hundred sixty-five million, six hundred sixty-one thousand, nine hundred one".