81705631 has 8 divisors (see below), whose sum is σ = 93450240. Its totient is φ = 69979128.

The previous prime is 81705623. The next prime is 81705653. The reversal of 81705631 is 13650718.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81705631 - 2³ = 81705623 is a prime.

It is a super-2 number, since 2×81705631² = 13351620274216322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81705593 and 81705602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81705691) 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, 7170 + ... + 14656.

It is an arithmetic number, because the mean of its divisors is an integer number (11681280).

Almost surely, 2^81705631 is an apocalyptic number.

81705631 is a deficient number, since it is larger than the sum of its proper divisors (11744609).

81705631 is a wasteful number, since it uses less digits than its factorization.

81705631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9053.

The product of its (nonzero) digits is 5040, while the sum is 31.

The square root of 81705631 is about 9039.1167156974. The cubic root of 81705631 is about 433.9276550539.

The spelling of 81705631 in words is "eighty-one million, seven hundred five thousand, six hundred thirty-one".