81211987 has 2 divisors, whose sum is σ = 81211988. Its totient is φ = 81211986.

The previous prime is 81211981. The next prime is 81212039. The reversal of 81211987 is 78911218.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81211987 is a prime.

It is not a weakly prime, because it can be changed into another prime (81211981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40605993 + 40605994.

It is an arithmetic number, because the mean of its divisors is an integer number (40605994).

Almost surely, 2^81211987 is an apocalyptic number.

81211987 is a deficient number, since it is larger than the sum of its proper divisors (1).

81211987 is an equidigital number, since it uses as much as digits as its factorization.

81211987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8064, while the sum is 37.

The square root of 81211987 is about 9011.7693601201. The cubic root of 81211987 is about 433.0519968066.

The spelling of 81211987 in words is "eighty-one million, two hundred eleven thousand, nine hundred eighty-seven".