201321818721 has 9 divisors (see below), whose sum is σ = 290800126929. Its totient is φ = 134213648436.

The previous prime is 201321818653. The next prime is 201321818741. The reversal of 201321818721 is 127818123102.

The square root of 201321818721 is 448689.

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

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 201321818721 - 2³³ = 192731884129 is a prime.

It is not an unprimeable number, because it can be changed into a prime (201321818741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1271286 + ... + 1420848.

Almost surely, 2^201321818721 is an apocalyptic number.

201321818721 is the 448689-th square number.

201321818721 is the 224345-th centered octagonal number.

It is an amenable number.

201321818721 is a deficient number, since it is larger than the sum of its proper divisors (89478308208).

201321818721 is an frugal number, since it uses more digits than its factorization.

201321818721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299132 (or 149566 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 36.

Multiplying 201321818721 by its sum of digits (36), we get a square (7247585473956 = 2692134²).

The spelling of 201321818721 in words is "two hundred one billion, three hundred twenty-one million, eight hundred eighteen thousand, seven hundred twenty-one".