393867952921 has 81 divisors (see below), whose sum is σ = 464259217149. Its totient is φ = 334017927936.

The previous prime is 393867952897. The next prime is 393867952939. The reversal of 393867952921 is 129259768393.

The square root of 393867952921 is 627589.

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

It can be written as a sum of positive squares in 4 ways, for example, as 38933209225 + 354934743696 = 197315^2 + 595764^2 .

It is a de Polignac number, because none of the positive numbers 2^k-393867952921 is a prime.

It is not an unprimeable number, because it can be changed into a prime (393867052921) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 5878626130 + ... + 5878626196.

Almost surely, 2^393867952921 is an apocalyptic number.

393867952921 is the 627589-th square number.

393867952921 is the 313795-th centered octagonal number.

It is an amenable number.

393867952921 is a deficient number, since it is larger than the sum of its proper divisors (70391264228).

393867952921 is an equidigital number, since it uses as much as digits as its factorization.

393867952921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264 (or 132 counting only the distinct ones).

The product of its digits is 44089920, while the sum is 64.

Multiplying 393867952921 by its sum of digits (64), we get a square (25207548986944 = 5020712²).

The spelling of 393867952921 in words is "three hundred ninety-three billion, eight hundred sixty-seven million, nine hundred fifty-two thousand, nine hundred twenty-one".