81406440 has 48 divisors (see below), whose sum is σ = 264572100. Its totient is φ = 21708288.

The previous prime is 81406417. The next prime is 81406441. The reversal of 81406440 is 4460418.

81406440 is a `hidden beast` number, since 8 + 14 + 0 + 644 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 79174404 + 2232036 = 8898^2 + 1494^2 .

It is not an unprimeable number, because it can be changed into a prime (81406441) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 112705 + ... + 113424.

Almost surely, 2^81406440 is an apocalyptic number.

It is an amenable number.

81406440 is an abundant number, since it is smaller than the sum of its proper divisors (183165660).

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

81406440 is a wasteful number, since it uses less digits than its factorization.

81406440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 226146 (or 226139 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 81406440 is about 9022.5517454875. The cubic root of 81406440 is about 433.3973528031.

Adding to 81406440 its reverse (4460418), we get a palindrome (85866858).

The spelling of 81406440 in words is "eighty-one million, four hundred six thousand, four hundred forty".