166749721 has 2 divisors, whose sum is σ = 166749722. Its totient is φ = 166749720.

The previous prime is 166749691. The next prime is 166749773. The reversal of 166749721 is 127947661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 152769600 + 13980121 = 12360^2 + 3739^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-166749721 is a prime.

It is not a weakly prime, because it can be changed into another prime (166749221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83374860 + 83374861.

It is an arithmetic number, because the mean of its divisors is an integer number (83374861).

Almost surely, 2^166749721 is an apocalyptic number.

It is an amenable number.

166749721 is a deficient number, since it is larger than the sum of its proper divisors (1).

166749721 is an equidigital number, since it uses as much as digits as its factorization.

166749721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 127008, while the sum is 43.

The square root of 166749721 is about 12913.1607672173. The cubic root of 166749721 is about 550.4126060909.

The spelling of 166749721 in words is "one hundred sixty-six million, seven hundred forty-nine thousand, seven hundred twenty-one".