221971957321 has 3 divisors (see below), whose sum is σ = 221972428461. Its totient is φ = 221971486182.

The previous prime is 221971957313. The next prime is 221971957327. The reversal of 221971957321 is 123759179122.

The square root of 221971957321 is 471139.

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 221971957321 - 2³ = 221971957313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221971957327) 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, 235570 + ... + 706708.

It is an arithmetic number, because the mean of its divisors is an integer number (73990809487).

Almost surely, 2^221971957321 is an apocalyptic number.

221971957321 is the 471139-th square number.

221971957321 is the 235570-th centered octagonal number.

It is an amenable number.

221971957321 is a deficient number, since it is larger than the sum of its proper divisors (471140).

221971957321 is an frugal number, since it uses more digits than its factorization.

221971957321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 942278 (or 471139 counting only the distinct ones).

The product of its digits is 476280, while the sum is 49.

Multiplying 221971957321 by its sum of digits (49), we get a square (10876625908729 = 3297973²).

The spelling of 221971957321 in words is "two hundred twenty-one billion, nine hundred seventy-one million, nine hundred fifty-seven thousand, three hundred twenty-one".