81521175739 has 2 divisors, whose sum is σ = 81521175740. Its totient is φ = 81521175738.

The previous prime is 81521175679. The next prime is 81521175761. The reversal of 81521175739 is 93757112518.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81521175739 - 2⁷ = 81521175611 is a prime.

It is a super-2 number, since 2×81521175739² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81521175692 and 81521175701.

It is not a weakly prime, because it can be changed into another prime (81521179739) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40760587869 + 40760587870.

It is an arithmetic number, because the mean of its divisors is an integer number (40760587870).

Almost surely, 2^81521175739 is an apocalyptic number.

81521175739 is a deficient number, since it is larger than the sum of its proper divisors (1).

81521175739 is an equidigital number, since it uses as much as digits as its factorization.

81521175739 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 529200, while the sum is 49.

The spelling of 81521175739 in words is "eighty-one billion, five hundred twenty-one million, one hundred seventy-five thousand, seven hundred thirty-nine".