999770021 has 2 divisors, whose sum is σ = 999770022. Its totient is φ = 999770020.

The previous prime is 999770011. The next prime is 999770029. The reversal of 999770021 is 120077999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 730350625 + 269419396 = 27025^2 + 16414^2 .

It is a cyclic number.

It is not a de Polignac number, because 999770021 - 2¹⁴ = 999753637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999770029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499885010 + 499885011.

It is an arithmetic number, because the mean of its divisors is an integer number (499885011).

Almost surely, 2^999770021 is an apocalyptic number.

It is an amenable number.

999770021 is a deficient number, since it is larger than the sum of its proper divisors (1).

999770021 is an equidigital number, since it uses as much as digits as its factorization.

999770021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 71442, while the sum is 44.

The square root of 999770021 is about 31619.1401053223. The cubic root of 999770021 is about 999.9233344559.

The spelling of 999770021 in words is "nine hundred ninety-nine million, seven hundred seventy thousand, twenty-one".