81887707861 has 2 divisors, whose sum is σ = 81887707862. Its totient is φ = 81887707860.

The previous prime is 81887707817. The next prime is 81887707873. The reversal of 81887707861 is 16870778818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72068087025 + 9819620836 = 268455^2 + 99094^2 .

It is a cyclic number.

It is not a de Polignac number, because 81887707861 - 2¹¹ = 81887705813 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81887707861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81887707261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40943853930 + 40943853931.

It is an arithmetic number, because the mean of its divisors is an integer number (40943853931).

Almost surely, 2^81887707861 is an apocalyptic number.

It is an amenable number.

81887707861 is a deficient number, since it is larger than the sum of its proper divisors (1).

81887707861 is an equidigital number, since it uses as much as digits as its factorization.

81887707861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8429568, while the sum is 61.

The spelling of 81887707861 in words is "eighty-one billion, eight hundred eighty-seven million, seven hundred seven thousand, eight hundred sixty-one".