81531907 has 8 divisors (see below), whose sum is σ = 85917200. Its totient is φ = 77156064.

The previous prime is 81531899. The next prime is 81531917. The reversal of 81531907 is 70913518.

It is a happy number.

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 81531907 - 2³ = 81531899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81531917) 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, 21769 + ... + 25237.

It is an arithmetic number, because the mean of its divisors is an integer number (10739650).

Almost surely, 2^81531907 is an apocalyptic number.

81531907 is a deficient number, since it is larger than the sum of its proper divisors (4385293).

81531907 is a wasteful number, since it uses less digits than its factorization.

81531907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4725.

The product of its (nonzero) digits is 7560, while the sum is 34.

The square root of 81531907 is about 9029.5020349962. The cubic root of 81531907 is about 433.6198952027.

The spelling of 81531907 in words is "eighty-one million, five hundred thirty-one thousand, nine hundred seven".