81379157861 has 2 divisors, whose sum is σ = 81379157862. Its totient is φ = 81379157860.

The previous prime is 81379157837. The next prime is 81379157891. The reversal of 81379157861 is 16875197318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75779628961 + 5599528900 = 275281^2 + 74830^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81379157861 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 81379157797 and 81379157806.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81379157891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40689578930 + 40689578931.

It is an arithmetic number, because the mean of its divisors is an integer number (40689578931).

Almost surely, 2^81379157861 is an apocalyptic number.

It is an amenable number.

81379157861 is a deficient number, since it is larger than the sum of its proper divisors (1).

81379157861 is an equidigital number, since it uses as much as digits as its factorization.

81379157861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2540160, while the sum is 56.

The spelling of 81379157861 in words is "eighty-one billion, three hundred seventy-nine million, one hundred fifty-seven thousand, eight hundred sixty-one".