81142021 has 2 divisors, whose sum is σ = 81142022. Its totient is φ = 81142020.

The previous prime is 81142001. The next prime is 81142031. The reversal of 81142021 is 12024118.

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., 70812225 + 10329796 = 8415^2 + 3214^2 .

It is a cyclic number.

It is not a de Polignac number, because 81142021 - 2⁹ = 81141509 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81142021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81142001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40571010 + 40571011.

It is an arithmetic number, because the mean of its divisors is an integer number (40571011).

Almost surely, 2^81142021 is an apocalyptic number.

It is an amenable number.

81142021 is a deficient number, since it is larger than the sum of its proper divisors (1).

81142021 is an equidigital number, since it uses as much as digits as its factorization.

81142021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 81142021 is about 9007.8866000855. The cubic root of 81142021 is about 432.9275996481.

Adding to 81142021 its reverse (12024118), we get a palindrome (93166139).

The spelling of 81142021 in words is "eighty-one million, one hundred forty-two thousand, twenty-one".