397638721 has 4 divisors (see below), whose sum is σ = 421029252. Its totient is φ = 374248192.

The previous prime is 397638713. The next prime is 397638727. The reversal of 397638721 is 127836793.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 210250000 + 187388721 = 14500^2 + 13689^2 .

It is a cyclic number.

It is not a de Polignac number, because 397638721 - 2³ = 397638713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (397638727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11695240 + ... + 11695273.

It is an arithmetic number, because the mean of its divisors is an integer number (105257313).

Almost surely, 2^397638721 is an apocalyptic number.

It is an amenable number.

397638721 is a deficient number, since it is larger than the sum of its proper divisors (23390531).

397638721 is a wasteful number, since it uses less digits than its factorization.

397638721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23390530.

The product of its digits is 381024, while the sum is 46.

The square root of 397638721 is about 19940.8806475542. The cubic root of 397638721 is about 735.3535997399.

It can be divided in two parts, 39763 and 8721, that added together give a palindrome (48484).

The spelling of 397638721 in words is "three hundred ninety-seven million, six hundred thirty-eight thousand, seven hundred twenty-one".