166123721 has 2 divisors, whose sum is σ = 166123722. Its totient is φ = 166123720.

The previous prime is 166123703. The next prime is 166123723. The reversal of 166123721 is 127321661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 162282121 + 3841600 = 12739^2 + 1960^2 .

It is an emirp because it is prime and its reverse (127321661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 166123721 - 2²⁶ = 99014857 is a prime.

Together with 166123723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (166123723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83061860 + 83061861.

It is an arithmetic number, because the mean of its divisors is an integer number (83061861).

Almost surely, 2^166123721 is an apocalyptic number.

It is an amenable number.

166123721 is a deficient number, since it is larger than the sum of its proper divisors (1).

166123721 is an equidigital number, since it uses as much as digits as its factorization.

166123721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 29.

The square root of 166123721 is about 12888.8991384059. The cubic root of 166123721 is about 549.7229690249.

The spelling of 166123721 in words is "one hundred sixty-six million, one hundred twenty-three thousand, seven hundred twenty-one".