81787943 has 4 divisors (see below), whose sum is σ = 83528160. Its totient is φ = 80047728.

The previous prime is 81787939. The next prime is 81787949. The reversal of 81787943 is 34978718.

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 81787943 - 2² = 81787939 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (47), and also a Moran number because the ratio is a prime number: 1740169 = 81787943 / (8 + 1 + 7 + 8 + 7 + 9 + 4 + 3).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81787949) 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, 870038 + ... + 870131.

It is an arithmetic number, because the mean of its divisors is an integer number (20882040).

Almost surely, 2^81787943 is an apocalyptic number.

81787943 is a deficient number, since it is larger than the sum of its proper divisors (1740217).

81787943 is a wasteful number, since it uses less digits than its factorization.

81787943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1740216.

The product of its digits is 338688, while the sum is 47.

The square root of 81787943 is about 9043.6686692957. The cubic root of 81787943 is about 434.0733221486.

The spelling of 81787943 in words is "eighty-one million, seven hundred eighty-seven thousand, nine hundred forty-three".