166721011 has 2 divisors, whose sum is σ = 166721012. Its totient is φ = 166721010.

The previous prime is 166720999. The next prime is 166721077. The reversal of 166721011 is 110127661.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 166721011 - 2⁵ = 166720979 is a prime.

It is not a weakly prime, because it can be changed into another prime (166721081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83360505 + 83360506.

It is an arithmetic number, because the mean of its divisors is an integer number (83360506).

Almost surely, 2^166721011 is an apocalyptic number.

166721011 is a deficient number, since it is larger than the sum of its proper divisors (1).

166721011 is an equidigital number, since it uses as much as digits as its factorization.

166721011 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504, while the sum is 25.

The square root of 166721011 is about 12912.0490627940. The cubic root of 166721011 is about 550.3810153276.

Adding to 166721011 its reverse (110127661), we get a palindrome (276848672).

The spelling of 166721011 in words is "one hundred sixty-six million, seven hundred twenty-one thousand, eleven".