81211573 has 2 divisors, whose sum is σ = 81211574. Its totient is φ = 81211572.

The previous prime is 81211523. The next prime is 81211591. The reversal of 81211573 is 37511218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53100369 + 28111204 = 7287^2 + 5302^2 .

It is a cyclic number.

It is not a de Polignac number, because 81211573 - 2²¹ = 79114421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81211523) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40605786 + 40605787.

It is an arithmetic number, because the mean of its divisors is an integer number (40605787).

Almost surely, 2^81211573 is an apocalyptic number.

It is an amenable number.

81211573 is a deficient number, since it is larger than the sum of its proper divisors (1).

81211573 is an equidigital number, since it uses as much as digits as its factorization.

81211573 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 28.

The square root of 81211573 is about 9011.7463901288. The cubic root of 81211573 is about 433.0512609389.

The spelling of 81211573 in words is "eighty-one million, two hundred eleven thousand, five hundred seventy-three".