165557021 has 8 divisors (see below), whose sum is σ = 190303104. Its totient is φ = 141084720.

The previous prime is 165557017. The next prime is 165557023. The reversal of 165557021 is 120755561.

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

It is not a de Polignac number, because 165557021 - 2² = 165557017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165557023) 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, 67145 + ... + 69566.

It is an arithmetic number, because the mean of its divisors is an integer number (23787888).

Almost surely, 2^165557021 is an apocalyptic number.

It is an amenable number.

165557021 is a deficient number, since it is larger than the sum of its proper divisors (24746083).

165557021 is a wasteful number, since it uses less digits than its factorization.

165557021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136891.

The product of its (nonzero) digits is 10500, while the sum is 32.

The square root of 165557021 is about 12866.8963235117. The cubic root of 165557021 is about 549.0971645193.

The spelling of 165557021 in words is "one hundred sixty-five million, five hundred fifty-seven thousand, twenty-one".