165615551 has 4 divisors (see below), whose sum is σ = 165956112. Its totient is φ = 165274992.

The previous prime is 165615511. The next prime is 165615553. The reversal of 165615551 is 155516561.

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

It is a cyclic number.

It is not a de Polignac number, because 165615551 - 2¹⁴ = 165599167 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 (165615553) 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, 169550 + ... + 170523.

It is an arithmetic number, because the mean of its divisors is an integer number (41489028).

Almost surely, 2^165615551 is an apocalyptic number.

165615551 is a deficient number, since it is larger than the sum of its proper divisors (340561).

165615551 is an equidigital number, since it uses as much as digits as its factorization.

165615551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 340560.

The product of its digits is 22500, while the sum is 35.

The square root of 165615551 is about 12869.1705637931. The cubic root of 165615551 is about 549.1618650280.

The spelling of 165615551 in words is "one hundred sixty-five million, six hundred fifteen thousand, five hundred fifty-one".