81630664 has 8 divisors (see below), whose sum is σ = 153057510. Its totient is φ = 40815328.

The previous prime is 81630643. The next prime is 81630667. The reversal of 81630664 is 46603618.

It can be written as a sum of positive squares in only one way, i.e., 75168900 + 6461764 = 8670^2 + 2542^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (81630667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5101909 + ... + 5101924.

Almost surely, 2^81630664 is an apocalyptic number.

It is an amenable number.

81630664 is a deficient number, since it is larger than the sum of its proper divisors (71426846).

81630664 is a wasteful number, since it uses less digits than its factorization.

81630664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10203839 (or 10203835 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 34.

The square root of 81630664 is about 9034.9689540142. The cubic root of 81630664 is about 433.7949012142.

The spelling of 81630664 in words is "eighty-one million, six hundred thirty thousand, six hundred sixty-four".