166721537 has 2 divisors, whose sum is σ = 166721538. Its totient is φ = 166721536.

The previous prime is 166721509. The next prime is 166721543. The reversal of 166721537 is 735127661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 113124496 + 53597041 = 10636^2 + 7321^2 .

It is a cyclic number.

It is not a de Polignac number, because 166721537 - 2⁸ = 166721281 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 166721537.

It is not a weakly prime, because it can be changed into another prime (166721557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83360768 + 83360769.

It is an arithmetic number, because the mean of its divisors is an integer number (83360769).

Almost surely, 2^166721537 is an apocalyptic number.

It is an amenable number.

166721537 is a deficient number, since it is larger than the sum of its proper divisors (1).

166721537 is an equidigital number, since it uses as much as digits as its factorization.

166721537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52920, while the sum is 38.

The square root of 166721537 is about 12912.0694313499. The cubic root of 166721537 is about 550.3815941391.

The spelling of 166721537 in words is "one hundred sixty-six million, seven hundred twenty-one thousand, five hundred thirty-seven".