20431557721 has 3 divisors (see below), whose sum is σ = 20431700661. Its totient is φ = 20431414782.

The previous prime is 20431557701. The next prime is 20431557733. The reversal of 20431557721 is 12775513402.

The square root of 20431557721 is 142939.

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 20431557721 - 2¹³ = 20431549529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20431557701) 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, 71470 + ... + 214408.

It is an arithmetic number, because the mean of its divisors is an integer number (6810566887).

Almost surely, 2^20431557721 is an apocalyptic number.

20431557721 is the 142939-th square number.

20431557721 is the 71470-th centered octagonal number.

It is an amenable number.

20431557721 is a deficient number, since it is larger than the sum of its proper divisors (142940).

20431557721 is an frugal number, since it uses more digits than its factorization.

20431557721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285878 (or 142939 counting only the distinct ones).

The product of its (nonzero) digits is 58800, while the sum is 37.

The spelling of 20431557721 in words is "twenty billion, four hundred thirty-one million, five hundred fifty-seven thousand, seven hundred twenty-one".