165697021 has 4 divisors (see below), whose sum is σ = 189368032. Its totient is φ = 142026012.

The previous prime is 165697019. The next prime is 165697057. The reversal of 165697021 is 120796561.

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, and also an emirpimes, since its reverse is a distinct semiprime: 120796561 = 281 ⋅429881.

It is a cyclic number.

It is not a de Polignac number, because 165697021 - 2¹ = 165697019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165697001) 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, 11835495 + ... + 11835508.

It is an arithmetic number, because the mean of its divisors is an integer number (47342008).

Almost surely, 2^165697021 is an apocalyptic number.

It is an amenable number.

165697021 is a deficient number, since it is larger than the sum of its proper divisors (23671011).

165697021 is an equidigital number, since it uses as much as digits as its factorization.

165697021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23671010.

The product of its (nonzero) digits is 22680, while the sum is 37.

The square root of 165697021 is about 12872.3354912774. The cubic root of 165697021 is about 549.2518986080.

The spelling of 165697021 in words is "one hundred sixty-five million, six hundred ninety-seven thousand, twenty-one".