81630961 has 2 divisors, whose sum is σ = 81630962. Its totient is φ = 81630960.

The previous prime is 81630953. The next prime is 81630977. The reversal of 81630961 is 16903618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73616400 + 8014561 = 8580^2 + 2831^2 .

It is a cyclic number.

It is not a de Polignac number, because 81630961 - 2³ = 81630953 is a prime.

It is a super-2 number, since 2×81630961² = 13327227587567042, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (81633961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40815480 + 40815481.

It is an arithmetic number, because the mean of its divisors is an integer number (40815481).

Almost surely, 2^81630961 is an apocalyptic number.

It is an amenable number.

81630961 is a deficient number, since it is larger than the sum of its proper divisors (1).

81630961 is an equidigital number, since it uses as much as digits as its factorization.

81630961 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 81630961 is about 9034.9853901376. The cubic root of 81630961 is about 433.7954273112.

The spelling of 81630961 in words is "eighty-one million, six hundred thirty thousand, nine hundred sixty-one".