159990821 has 2 divisors, whose sum is σ = 159990822. Its totient is φ = 159990820.

The previous prime is 159990799. The next prime is 159990833. The reversal of 159990821 is 128099951.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 103530625 + 56460196 = 10175^2 + 7514^2 .

It is a cyclic number.

It is not a de Polignac number, because 159990821 - 2¹⁸ = 159728677 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (159990871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 79995410 + 79995411.

It is an arithmetic number, because the mean of its divisors is an integer number (79995411).

Almost surely, 2^159990821 is an apocalyptic number.

It is an amenable number.

159990821 is a deficient number, since it is larger than the sum of its proper divisors (1).

159990821 is an equidigital number, since it uses as much as digits as its factorization.

159990821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 58320, while the sum is 44.

The square root of 159990821 is about 12648.7478036365. The cubic root of 159990821 is about 542.8731416041.

The spelling of 159990821 in words is "one hundred fifty-nine million, nine hundred ninety thousand, eight hundred twenty-one".