81631211 has 2 divisors, whose sum is σ = 81631212. Its totient is φ = 81631210.

The previous prime is 81631171. The next prime is 81631217. The reversal of 81631211 is 11213618.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81631211 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81631217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40815605 + 40815606.

It is an arithmetic number, because the mean of its divisors is an integer number (40815606).

Almost surely, 2^81631211 is an apocalyptic number.

81631211 is a deficient number, since it is larger than the sum of its proper divisors (1).

81631211 is an equidigital number, since it uses as much as digits as its factorization.

81631211 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 23.

The square root of 81631211 is about 9034.9992252352. Note that the first 3 decimals coincide. The cubic root of 81631211 is about 433.7958701528.

Adding to 81631211 its reverse (11213618), we get a palindrome (92844829).

The spelling of 81631211 in words is "eighty-one million, six hundred thirty-one thousand, two hundred eleven".