81021697 has 2 divisors, whose sum is σ = 81021698. Its totient is φ = 81021696.

The previous prime is 81021671. The next prime is 81021701. The reversal of 81021697 is 79612018.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61449921 + 19571776 = 7839^2 + 4424^2 .

It is a cyclic number.

It is not a de Polignac number, because 81021697 - 2¹⁹ = 80497409 is a prime.

It is not a weakly prime, because it can be changed into another prime (81021097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40510848 + 40510849.

It is an arithmetic number, because the mean of its divisors is an integer number (40510849).

Almost surely, 2^81021697 is an apocalyptic number.

It is an amenable number.

81021697 is a deficient number, since it is larger than the sum of its proper divisors (1).

81021697 is an equidigital number, since it uses as much as digits as its factorization.

81021697 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 81021697 is about 9001.2053081796. The cubic root of 81021697 is about 432.7135003457.

It can be divided in two parts, 81021 and 697, that added together give a palindrome (81718).

The spelling of 81021697 in words is "eighty-one million, twenty-one thousand, six hundred ninety-seven".