166540721 has 8 divisors (see below), whose sum is σ = 176454144. Its totient is φ = 156640320.

The previous prime is 166540691. The next prime is 166540739. The reversal of 166540721 is 127045661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 166540721 - 2¹⁸ = 166278577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166540741) 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, 38456 + ... + 42566.

It is an arithmetic number, because the mean of its divisors is an integer number (22056768).

Almost surely, 2^166540721 is an apocalyptic number.

It is an amenable number.

166540721 is a deficient number, since it is larger than the sum of its proper divisors (9913423).

166540721 is a wasteful number, since it uses less digits than its factorization.

166540721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6511.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 166540721 is about 12905.0657107974. The cubic root of 166540721 is about 550.1825520741.

The spelling of 166540721 in words is "one hundred sixty-six million, five hundred forty thousand, seven hundred twenty-one".