165221551 has 4 divisors (see below), whose sum is σ = 180241704. Its totient is φ = 150201400.

The previous prime is 165221533. The next prime is 165221561. The reversal of 165221551 is 155122561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 155122561 = 11 ⋅14102051.

It is a cyclic number.

It is not a de Polignac number, because 165221551 - 2⁵ = 165221519 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 (165221501) 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, 7510060 + ... + 7510081.

It is an arithmetic number, because the mean of its divisors is an integer number (45060426).

Almost surely, 2^165221551 is an apocalyptic number.

165221551 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

165221551 is a deficient number, since it is larger than the sum of its proper divisors (15020153).

165221551 is a wasteful number, since it uses less digits than its factorization.

165221551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15020152.

The product of its digits is 3000, while the sum is 28.

The square root of 165221551 is about 12853.8535466995. The cubic root of 165221551 is about 548.7260332031.

The spelling of 165221551 in words is "one hundred sixty-five million, two hundred twenty-one thousand, five hundred fifty-one".