81951906 has 16 divisors (see below), whose sum is σ = 164022624. Its totient is φ = 27297504.

The previous prime is 81951889. The next prime is 81951911. The reversal of 81951906 is 60915918.

It is a super-2 number, since 2×81951906² = 13432229794065672, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5821 + ... + 14063.

It is an arithmetic number, because the mean of its divisors is an integer number (10251414).

Almost surely, 2^81951906 is an apocalyptic number.

81951906 is an abundant number, since it is smaller than the sum of its proper divisors (82070718).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81951906 is a wasteful number, since it uses less digits than its factorization.

81951906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9905.

The product of its (nonzero) digits is 19440, while the sum is 39.

The square root of 81951906 is about 9052.7292017380. The cubic root of 81951906 is about 434.3631955869.

It can be divided in two parts, 8195 and 1906, that added together give a palindrome (10101).

The spelling of 81951906 in words is "eighty-one million, nine hundred fifty-one thousand, nine hundred six".