81047720 has 32 divisors (see below), whose sum is σ = 196386120. Its totient is φ = 29925120.

The previous prime is 81047669. The next prime is 81047731. The reversal of 81047720 is 2774018.

It can be written as a sum of positive squares in 4 ways, for example, as 72556324 + 8491396 = 8518^2 + 2914^2 .

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 7 ways as a sum of consecutive naturals, for example, 77411 + ... + 78450.

Almost surely, 2^81047720 is an apocalyptic number.

It is an amenable number.

81047720 is an abundant number, since it is smaller than the sum of its proper divisors (115338400).

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

81047720 is a wasteful number, since it uses less digits than its factorization.

81047720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155885 (or 155881 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 29.

The square root of 81047720 is about 9002.6507207600. The cubic root of 81047720 is about 432.7598224976.

The spelling of 81047720 in words is "eighty-one million, forty-seven thousand, seven hundred twenty".