165719821 has 2 divisors, whose sum is σ = 165719822. Its totient is φ = 165719820.

The previous prime is 165719809. The next prime is 165719857. The reversal of 165719821 is 128917561.

It is a happy number.

165719821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 152250921 + 13468900 = 12339^2 + 3670^2 .

It is a cyclic number.

It is not a de Polignac number, because 165719821 - 2⁵ = 165719789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165719861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82859910 + 82859911.

It is an arithmetic number, because the mean of its divisors is an integer number (82859911).

Almost surely, 2^165719821 is an apocalyptic number.

It is an amenable number.

165719821 is a deficient number, since it is larger than the sum of its proper divisors (1).

165719821 is an equidigital number, since it uses as much as digits as its factorization.

165719821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 40.

The square root of 165719821 is about 12873.2210809882. The cubic root of 165719821 is about 549.2770899057.

The spelling of 165719821 in words is "one hundred sixty-five million, seven hundred nineteen thousand, eight hundred twenty-one".