81606547720 has 32 divisors (see below), whose sum is σ = 194415600600. Its totient is φ = 30722464768.

The previous prime is 81606547697. The next prime is 81606547741. The reversal of 81606547720 is 2774560618.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 81554794084 + 51753636 = 285578^2 + 7194^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 60004135 + ... + 60005494.

Almost surely, 2^81606547720 is an apocalyptic number.

It is an amenable number.

81606547720 is an abundant number, since it is smaller than the sum of its proper divisors (112809052880).

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

81606547720 is a wasteful number, since it uses less digits than its factorization.

81606547720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120009657 (or 120009653 counting only the distinct ones).

The product of its (nonzero) digits is 564480, while the sum is 46.

The spelling of 81606547720 in words is "eighty-one billion, six hundred six million, five hundred forty-seven thousand, seven hundred twenty".