393958330921 has 3 divisors (see below), whose sum is σ = 393958958583. Its totient is φ = 393957703260.

The previous prime is 393958330903. The next prime is 393958330937. The reversal of 393958330921 is 129033859393.

The square root of 393958330921 is 627661.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 129033859393 = 113 ⋅1141892561.

It can be written as a sum of positive squares in only one way, i.e., 294619898521 + 99338432400 = 542789^2 + 315180^2 .

It is not a de Polignac number, because 393958330921 - 2⁵ = 393958330889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (393958330901) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 313831 + ... + 941491.

It is an arithmetic number, because the mean of its divisors is an integer number (131319652861).

Almost surely, 2^393958330921 is an apocalyptic number.

393958330921 is the 627661-st square number.

393958330921 is the 313831-st centered octagonal number.

It is an amenable number.

393958330921 is a deficient number, since it is larger than the sum of its proper divisors (627662).

393958330921 is an frugal number, since it uses more digits than its factorization.

393958330921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1255322 (or 627661 counting only the distinct ones).

The product of its (nonzero) digits is 4723920, while the sum is 55.

The spelling of 393958330921 in words is "three hundred ninety-three billion, nine hundred fifty-eight million, three hundred thirty thousand, nine hundred twenty-one".