165694021 has 4 divisors (see below), whose sum is σ = 166063500. Its totient is φ = 165324544.

The previous prime is 165693991. The next prime is 165694051. The reversal of 165694021 is 120496561.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (165693991) and next prime (165694051).

It can be written as a sum of positive squares in 2 ways, for example, as 104244100 + 61449921 = 10210^2 + 7839^2 .

It is a cyclic number.

It is not a de Polignac number, because 165694021 - 2¹³ = 165685829 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 (165694051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 184066 + ... + 184963.

It is an arithmetic number, because the mean of its divisors is an integer number (41515875).

Almost surely, 2^165694021 is an apocalyptic number.

It is an amenable number.

165694021 is a deficient number, since it is larger than the sum of its proper divisors (369479).

165694021 is an equidigital number, since it uses as much as digits as its factorization.

165694021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369478.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 165694021 is about 12872.2189617797. The cubic root of 165694021 is about 549.2485837916.

The spelling of 165694021 in words is "one hundred sixty-five million, six hundred ninety-four thousand, twenty-one".