81851211 has 48 divisors (see below), whose sum is σ = 132455232. Its totient is φ = 48384000.

The previous prime is 81851207. The next prime is 81851233. The reversal of 81851211 is 11215818.

It is not a de Polignac number, because 81851211 - 2² = 81851207 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (81851201) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 541986 + ... + 542136.

It is an arithmetic number, because the mean of its divisors is an integer number (2759484).

Almost surely, 2^81851211 is an apocalyptic number.

81851211 is a deficient number, since it is larger than the sum of its proper divisors (50604021).

81851211 is a wasteful number, since it uses less digits than its factorization.

81851211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324 (or 321 counting only the distinct ones).

The product of its digits is 640, while the sum is 27.

The square root of 81851211 is about 9047.1659098305. The cubic root of 81851211 is about 434.1852207633.

The spelling of 81851211 in words is "eighty-one million, eight hundred fifty-one thousand, two hundred eleven".