185900021 has 2 divisors, whose sum is σ = 185900022. Its totient is φ = 185900020.

The previous prime is 185899979. The next prime is 185900023. The reversal of 185900021 is 120009581.

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., 176597521 + 9302500 = 13289^2 + 3050^2 .

It is a cyclic number.

It is not a de Polignac number, because 185900021 - 2¹⁰ = 185898997 is a prime.

It is a Sophie Germain prime.

Together with 185900023, it forms a pair of twin primes.

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 (185900023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 92950010 + 92950011.

It is an arithmetic number, because the mean of its divisors is an integer number (92950011).

Almost surely, 2^185900021 is an apocalyptic number.

It is an amenable number.

185900021 is a deficient number, since it is larger than the sum of its proper divisors (1).

185900021 is an equidigital number, since it uses as much as digits as its factorization.

185900021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 185900021 is about 13634.5157963163. The cubic root of 185900021 is about 570.7244517901.

The spelling of 185900021 in words is "one hundred eighty-five million, nine hundred thousand, twenty-one".