81821371 has 2 divisors, whose sum is σ = 81821372. Its totient is φ = 81821370.

The previous prime is 81821359. The next prime is 81821387. The reversal of 81821371 is 17312818.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81821371 - 2⁵ = 81821339 is a prime.

It is not a weakly prime, because it can be changed into another prime (81825371) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40910685 + 40910686.

It is an arithmetic number, because the mean of its divisors is an integer number (40910686).

Almost surely, 2^81821371 is an apocalyptic number.

81821371 is a deficient number, since it is larger than the sum of its proper divisors (1).

81821371 is an equidigital number, since it uses as much as digits as its factorization.

81821371 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 31.

The square root of 81821371 is about 9045.5166242730. The cubic root of 81821371 is about 434.1324515919.

The spelling of 81821371 in words is "eighty-one million, eight hundred twenty-one thousand, three hundred seventy-one".