81047640 has 64 divisors (see below), whose sum is σ = 250997760. Its totient is φ = 20914560.

The previous prime is 81047633. The next prime is 81047657. The reversal of 81047640 is 4674018.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81047598 and 81047607.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 7174 + ... + 14613.

It is an arithmetic number, because the mean of its divisors is an integer number (3921840).

Almost surely, 2^81047640 is an apocalyptic number.

It is an amenable number.

81047640 is an abundant number, since it is smaller than the sum of its proper divisors (169950120).

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

81047640 is a wasteful number, since it uses less digits than its factorization.

81047640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21832 (or 21828 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 81047640 is about 9002.6462776230. The cubic root of 81047640 is about 432.7596801090.

The spelling of 81047640 in words is "eighty-one million, forty-seven thousand, six hundred forty".