81964725221 has 8 divisors (see below), whose sum is σ = 82088384664. Its totient is φ = 81841132800.

The previous prime is 81964725151. The next prime is 81964725239. The reversal of 81964725221 is 12252746918.

It can be written as a sum of positive squares in 4 ways, for example, as 40798344196 + 41166381025 = 201986^2 + 202895^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81964725221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81964725251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2773121 + ... + 2802521.

It is an arithmetic number, because the mean of its divisors is an integer number (10261048083).

Almost surely, 2^81964725221 is an apocalyptic number.

It is an amenable number.

81964725221 is a deficient number, since it is larger than the sum of its proper divisors (123659443).

81964725221 is a wasteful number, since it uses less digits than its factorization.

81964725221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33511.

The product of its digits is 483840, while the sum is 47.

The spelling of 81964725221 in words is "eighty-one billion, nine hundred sixty-four million, seven hundred twenty-five thousand, two hundred twenty-one".