165621506 has 4 divisors (see below), whose sum is σ = 248432262. Its totient is φ = 82810752.

The previous prime is 165621457. The next prime is 165621553. The reversal of 165621506 is 605126561.

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

It can be written as a sum of positive squares in only one way, i.e., 117527281 + 48094225 = 10841^2 + 6935^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41405375 + ... + 41405378.

Almost surely, 2^165621506 is an apocalyptic number.

165621506 is a deficient number, since it is larger than the sum of its proper divisors (82810756).

165621506 is an equidigital number, since it uses as much as digits as its factorization.

165621506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82810755.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 165621506 is about 12869.4019286057. The cubic root of 165621506 is about 549.1684469777.

The spelling of 165621506 in words is "one hundred sixty-five million, six hundred twenty-one thousand, five hundred six".