165495189721 has 3 divisors (see below), whose sum is σ = 165495596533. Its totient is φ = 165494782910.

The previous prime is 165495189677. The next prime is 165495189781. The reversal of 165495189721 is 127981594561.

The square root of 165495189721 is 406811.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 165495189721 - 2¹⁹ = 165494665433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165495189781) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 203406 + ... + 610216.

Almost surely, 2^165495189721 is an apocalyptic number.

165495189721 is the 406811-st square number.

165495189721 is the 203406-th centered octagonal number.

It is an amenable number.

165495189721 is a deficient number, since it is larger than the sum of its proper divisors (406812).

165495189721 is an frugal number, since it uses more digits than its factorization.

165495189721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 813622 (or 406811 counting only the distinct ones).

The product of its digits is 5443200, while the sum is 58.

It can be divided in two parts, 165495 and 189721, that added together give a square (355216 = 596²).

The spelling of 165495189721 in words is "one hundred sixty-five billion, four hundred ninety-five million, one hundred eighty-nine thousand, seven hundred twenty-one".