81664224 has 96 divisors (see below), whose sum is σ = 223179264. Its totient is φ = 26127360.

The previous prime is 81664211. The next prime is 81664241. The reversal of 81664224 is 42246618.

It is a tau number, because it is divible by the number of its divisors (96).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 301209 + ... + 301479.

It is an arithmetic number, because the mean of its divisors is an integer number (2324784).

Almost surely, 2^81664224 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 81664224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (111589632).

81664224 is an abundant number, since it is smaller than the sum of its proper divisors (141515040).

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

81664224 is a wasteful number, since it uses less digits than its factorization.

81664224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400 (or 392 counting only the distinct ones).

The product of its digits is 18432, while the sum is 33.

The square root of 81664224 is about 9036.8259914640. The cubic root of 81664224 is about 433.8543403252.

The spelling of 81664224 in words is "eighty-one million, six hundred sixty-four thousand, two hundred twenty-four".