195721573621 has 6 divisors (see below), whose sum is σ = 227676116310. Its totient is φ = 167761348776.

The previous prime is 195721573609. The next prime is 195721573703. The reversal of 195721573621 is 126375127591.

It can be written as a sum of positive squares in only one way, i.e., 195705372996 + 16200625 = 442386^2 + 4025^2 .

It is not a de Polignac number, because 195721573621 - 2¹⁷ = 195721442549 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49), and also a Moran number because the ratio is a prime number: 3994317829 = 195721573621 / (1 + 9 + 5 + 7 + 2 + 1 + 5 + 7 + 3 + 6 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (195721573601) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1997158866 + ... + 1997158963.

It is an arithmetic number, because the mean of its divisors is an integer number (37946019385).

Almost surely, 2^195721573621 is an apocalyptic number.

It is an amenable number.

195721573621 is a deficient number, since it is larger than the sum of its proper divisors (31954542689).

195721573621 is an equidigital number, since it uses as much as digits as its factorization.

195721573621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3994317843 (or 3994317836 counting only the distinct ones).

The product of its digits is 793800, while the sum is 49.

The spelling of 195721573621 in words is "one hundred ninety-five billion, seven hundred twenty-one million, five hundred seventy-three thousand, six hundred twenty-one".