81628664 has 32 divisors (see below), whose sum is σ = 166698000. Its totient is φ = 37247232.

The previous prime is 81628661. The next prime is 81628667. The reversal of 81628664 is 46682618.

It is an interprime number because it is at equal distance from previous prime (81628661) and next prime (81628667).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81628661) 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, 4847 + ... + 13665.

Almost surely, 2^81628664 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 81628664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (83349000).

81628664 is an abundant number, since it is smaller than the sum of its proper divisors (85069336).

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

81628664 is a wasteful number, since it uses less digits than its factorization.

81628664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8927 (or 8923 counting only the distinct ones).

The product of its digits is 110592, while the sum is 41.

The square root of 81628664 is about 9034.8582722697. The cubic root of 81628664 is about 433.7913584406.

The spelling of 81628664 in words is "eighty-one million, six hundred twenty-eight thousand, six hundred sixty-four".