81806953 has 4 divisors (see below), whose sum is σ = 82007380. Its totient is φ = 81606528.

The previous prime is 81806927. The next prime is 81806969. The reversal of 81806953 is 35960818.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 41319184 + 40487769 = 6428^2 + 6363^2 .

It is a cyclic number.

It is not a de Polignac number, because 81806953 - 2²¹ = 79709801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81806993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99600 + ... + 100417.

It is an arithmetic number, because the mean of its divisors is an integer number (20501845).

Almost surely, 2^81806953 is an apocalyptic number.

It is an amenable number.

81806953 is a deficient number, since it is larger than the sum of its proper divisors (200427).

81806953 is a wasteful number, since it uses less digits than its factorization.

81806953 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200426.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81806953 is about 9044.7196197560. The cubic root of 81806953 is about 434.1069501477.

The spelling of 81806953 in words is "eighty-one million, eight hundred six thousand, nine hundred fifty-three".