81638805626879 has 2 divisors, whose sum is σ = 81638805626880. Its totient is φ = 81638805626878.

The previous prime is 81638805626837. The next prime is 81638805626881. The reversal of 81638805626879 is 97862650883618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81638805626879 - 2¹² = 81638805622783 is a prime.

It is a super-4 number, since 4×81638805626879⁴ (a number of 57 digits) contains 4444 as substring.

It is a Sophie Germain prime.

Together with 81638805626881, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81638805656879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40819402813439 + 40819402813440.

It is an arithmetic number, because the mean of its divisors is an integer number (40819402813440).

Almost surely, 2^{81638805626879} is an apocalyptic number.

81638805626879 is a deficient number, since it is larger than the sum of its proper divisors (1).

81638805626879 is an equidigital number, since it uses as much as digits as its factorization.

81638805626879 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1672151040, while the sum is 77.

The spelling of 81638805626879 in words is "eighty-one trillion, six hundred thirty-eight billion, eight hundred five million, six hundred twenty-six thousand, eight hundred seventy-nine".