538666455721 has 3 divisors (see below), whose sum is σ = 538667189661. Its totient is φ = 538665721782.

The previous prime is 538666455697. The next prime is 538666455731. The reversal of 538666455721 is 127554666835.

It is a happy number.

The square root of 538666455721 is 733939.

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.

It is not a de Polignac number, because 538666455721 - 2⁵ = 538666455689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (538666455731) 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, 366970 + ... + 1100908.

It is an arithmetic number, because the mean of its divisors is an integer number (179555729887).

Almost surely, 2^538666455721 is an apocalyptic number.

538666455721 is the 733939-th square number.

538666455721 is the 366970-th centered octagonal number.

It is an amenable number.

538666455721 is a deficient number, since it is larger than the sum of its proper divisors (733940).

538666455721 is an frugal number, since it uses more digits than its factorization.

538666455721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1467878 (or 733939 counting only the distinct ones).

The product of its digits is 36288000, while the sum is 58.

The spelling of 538666455721 in words is "five hundred thirty-eight billion, six hundred sixty-six million, four hundred fifty-five thousand, seven hundred twenty-one".