81906641 has 16 divisors (see below), whose sum is σ = 86184000. Its totient is φ = 77767488.

The previous prime is 81906637. The next prime is 81906667. The reversal of 81906641 is 14660918.

It is not a de Polignac number, because 81906641 - 2² = 81906637 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81906631) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 457490 + ... + 457668.

It is an arithmetic number, because the mean of its divisors is an integer number (5386500).

Almost surely, 2^81906641 is an apocalyptic number.

It is an amenable number.

81906641 is a deficient number, since it is larger than the sum of its proper divisors (4277359).

81906641 is a wasteful number, since it uses less digits than its factorization.

81906641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 448.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 81906641 is about 9050.2287816386. The cubic root of 81906641 is about 434.2832093608.

The spelling of 81906641 in words is "eighty-one million, nine hundred six thousand, six hundred forty-one".