166121661 has 4 divisors (see below), whose sum is σ = 221495552. Its totient is φ = 110747772.

The previous prime is 166121633. The next prime is 166121689.

166121661 is nontrivially palindromic in base 10.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (166121633) and next prime (166121689).

It is not a de Polignac number, because 166121661 - 2⁶ = 166121597 is a prime.

It is a super-3 number, since 3×166121661³ (a number of 26 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166121261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27686941 + ... + 27686946.

It is an arithmetic number, because the mean of its divisors is an integer number (55373888).

Almost surely, 2^166121661 is an apocalyptic number.

It is an amenable number.

166121661 is a deficient number, since it is larger than the sum of its proper divisors (55373891).

166121661 is an equidigital number, since it uses as much as digits as its factorization.

166121661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55373890.

The product of its digits is 2592, while the sum is 30.

The square root of 166121661 is about 12888.8192244286. The cubic root of 166121661 is about 549.7206967546.

The spelling of 166121661 in words is "one hundred sixty-six million, one hundred twenty-one thousand, six hundred sixty-one".