81861907 has 2 divisors, whose sum is σ = 81861908. Its totient is φ = 81861906.

The previous prime is 81861887. The next prime is 81861911. The reversal of 81861907 is 70916818.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81861907 - 2⁷ = 81861779 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81861907.

It is not a weakly prime, because it can be changed into another prime (81861977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40930953 + 40930954.

It is an arithmetic number, because the mean of its divisors is an integer number (40930954).

Almost surely, 2^81861907 is an apocalyptic number.

81861907 is a deficient number, since it is larger than the sum of its proper divisors (1).

81861907 is an equidigital number, since it uses as much as digits as its factorization.

81861907 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 81861907 is about 9047.7570148629. The cubic root of 81861907 is about 434.2041324886.

The spelling of 81861907 in words is "eighty-one million, eight hundred sixty-one thousand, nine hundred seven".