166721998 has 16 divisors (see below), whose sum is σ = 263535120. Its totient is φ = 78886656.

The previous prime is 166721993. The next prime is 166722007. The reversal of 166721998 is 899127661.

It is a super-2 number, since 2×166721998² = 55592449234224008, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166721993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44286 + ... + 47902.

It is an arithmetic number, because the mean of its divisors is an integer number (16470945).

Almost surely, 2^166721998 is an apocalyptic number.

166721998 is a deficient number, since it is larger than the sum of its proper divisors (96813122).

166721998 is a wasteful number, since it uses less digits than its factorization.

166721998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4851.

The product of its digits is 326592, while the sum is 49.

The square root of 166721998 is about 12912.0872828525. The cubic root of 166721998 is about 550.3821014234.

The spelling of 166721998 in words is "one hundred sixty-six million, seven hundred twenty-one thousand, nine hundred ninety-eight".