165620021 has 8 divisors (see below), whose sum is σ = 192488640. Its totient is φ = 139553568.

The previous prime is 165620003. The next prime is 165620023. The reversal of 165620021 is 120026561.

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

It is a de Polignac number, because none of the positive numbers 2^k-165620021 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 (165620023) 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, 200096 + ... + 200921.

It is an arithmetic number, because the mean of its divisors is an integer number (24061080).

Almost surely, 2^165620021 is an apocalyptic number.

It is an amenable number.

165620021 is a deficient number, since it is larger than the sum of its proper divisors (26868619).

165620021 is an equidigital number, since it uses as much as digits as its factorization.

165620021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 401083.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 165620021 is about 12869.3442334876. The cubic root of 165620021 is about 549.1668056499.

Adding to 165620021 its reverse (120026561), we get a palindrome (285646582).

The spelling of 165620021 in words is "one hundred sixty-five million, six hundred twenty thousand, twenty-one".