81632230721 has 4 divisors (see below), whose sum is σ = 81634224852. Its totient is φ = 81630236592.

The previous prime is 81632230717. The next prime is 81632230787. The reversal of 81632230721 is 12703223618.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19250175025 + 62382055696 = 138745^2 + 249764^2 .

It is a cyclic number.

It is not a de Polignac number, because 81632230721 - 2² = 81632230717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81632230321) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 934346 + ... + 1017971.

It is an arithmetic number, because the mean of its divisors is an integer number (20408556213).

Almost surely, 2^81632230721 is an apocalyptic number.

It is an amenable number.

81632230721 is a deficient number, since it is larger than the sum of its proper divisors (1994131).

81632230721 is a wasteful number, since it uses less digits than its factorization.

81632230721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1994130.

The product of its (nonzero) digits is 24192, while the sum is 35.

The spelling of 81632230721 in words is "eighty-one billion, six hundred thirty-two million, two hundred thirty thousand, seven hundred twenty-one".