81643253632 has 64 divisors (see below), whose sum is σ = 168790456800. Its totient is φ = 39289083904.

The previous prime is 81643253621. The next prime is 81643253639. The reversal of 81643253632 is 23635234618.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81643253639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1142013 + ... + 1211395.

Almost surely, 2^81643253632 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81643253632, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (84395228400).

81643253632 is an abundant number, since it is smaller than the sum of its proper divisors (87147203168).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81643253632 is a wasteful number, since it uses less digits than its factorization.

81643253632 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69743 (or 69731 counting only the distinct ones).

The product of its digits is 622080, while the sum is 43.

The spelling of 81643253632 in words is "eighty-one billion, six hundred forty-three million, two hundred fifty-three thousand, six hundred thirty-two".