81100631 has 4 divisors (see below), whose sum is σ = 81159600. Its totient is φ = 81041664.

The previous prime is 81100609. The next prime is 81100637. The reversal of 81100631 is 13600118.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81100631 - 2¹⁰ = 81099607 is a prime.

It is a super-2 number, since 2×81100631² = 13154624697196322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81100637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27371 + ... + 30188.

It is an arithmetic number, because the mean of its divisors is an integer number (20289900).

Almost surely, 2^81100631 is an apocalyptic number.

81100631 is a deficient number, since it is larger than the sum of its proper divisors (58969).

81100631 is a wasteful number, since it uses less digits than its factorization.

81100631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58968.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 81100631 is about 9005.5888758037. The cubic root of 81100631 is about 432.8539759746.

Adding to 81100631 its reverse (13600118), we get a palindrome (94700749).

The spelling of 81100631 in words is "eighty-one million, one hundred thousand, six hundred thirty-one".