81121751 has 2 divisors, whose sum is σ = 81121752. Its totient is φ = 81121750.

The previous prime is 81121721. The next prime is 81121757. The reversal of 81121751 is 15712118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81121751 - 2⁶ = 81121687 is a prime.

It is a super-3 number, since 3×81121751³ (a number of 25 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81121751.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81121757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40560875 + 40560876.

It is an arithmetic number, because the mean of its divisors is an integer number (40560876).

Almost surely, 2^81121751 is an apocalyptic number.

81121751 is a deficient number, since it is larger than the sum of its proper divisors (1).

81121751 is an equidigital number, since it uses as much as digits as its factorization.

81121751 is an evil number, because the sum of its binary digits is even.

The product of its digits is 560, while the sum is 26.

The square root of 81121751 is about 9006.7614046337. The cubic root of 81121751 is about 432.8915469216.

Adding to 81121751 its reverse (15712118), we get a palindrome (96833869).

The spelling of 81121751 in words is "eighty-one million, one hundred twenty-one thousand, seven hundred fifty-one".