81861887 has 2 divisors, whose sum is σ = 81861888. Its totient is φ = 81861886.

The previous prime is 81861883. The next prime is 81861907. The reversal of 81861887 is 78816818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81861887 - 2² = 81861883 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81861883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40930943 + 40930944.

It is an arithmetic number, because the mean of its divisors is an integer number (40930944).

Almost surely, 2^81861887 is an apocalyptic number.

81861887 is a deficient number, since it is larger than the sum of its proper divisors (1).

81861887 is an equidigital number, since it uses as much as digits as its factorization.

81861887 is an evil number, because the sum of its binary digits is even.

The product of its digits is 172032, while the sum is 47.

The square root of 81861887 is about 9047.7559096165. The cubic root of 81861887 is about 434.2040971279.

The spelling of 81861887 in words is "eighty-one million, eight hundred sixty-one thousand, eight hundred eighty-seven".