81021973 has 2 divisors, whose sum is σ = 81021974. Its totient is φ = 81021972.

The previous prime is 81021959. The next prime is 81021977. The reversal of 81021973 is 37912018.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78535044 + 2486929 = 8862^2 + 1577^2 .

It is a cyclic number.

It is not a de Polignac number, because 81021973 - 2¹³ = 81013781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81021977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40510986 + 40510987.

It is an arithmetic number, because the mean of its divisors is an integer number (40510987).

Almost surely, 2^81021973 is an apocalyptic number.

It is an amenable number.

81021973 is a deficient number, since it is larger than the sum of its proper divisors (1).

81021973 is an equidigital number, since it uses as much as digits as its factorization.

81021973 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 81021973 is about 9001.2206394466. The cubic root of 81021973 is about 432.7139916906.

The spelling of 81021973 in words is "eighty-one million, twenty-one thousand, nine hundred seventy-three".