81951287 has 4 divisors (see below), whose sum is σ = 89401416. Its totient is φ = 74501160.

The previous prime is 81951241. The next prime is 81951293. The reversal of 81951287 is 78215918.

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 81951287 - 2¹⁰ = 81950263 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81951217) 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, 3725048 + ... + 3725069.

It is an arithmetic number, because the mean of its divisors is an integer number (22350354).

Almost surely, 2^81951287 is an apocalyptic number.

81951287 is a deficient number, since it is larger than the sum of its proper divisors (7450129).

81951287 is a wasteful number, since it uses less digits than its factorization.

81951287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7450128.

The product of its digits is 40320, while the sum is 41.

The square root of 81951287 is about 9052.6950130886. The cubic root of 81951287 is about 434.3621019720.

The spelling of 81951287 in words is "eighty-one million, nine hundred fifty-one thousand, two hundred eighty-seven".