81707540 has 12 divisors (see below), whose sum is σ = 171585876. Its totient is φ = 32683008.

The previous prime is 81707539. The next prime is 81707551. The reversal of 81707540 is 4570718.

It can be written as a sum of positive squares in 2 ways, for example, as 13512976 + 68194564 = 3676^2 + 8258^2 .

It is a super-2 number, since 2×81707540² = 13352244185703200, which contains 22 as substring.

It is a plaindrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 81707497 and 81707506.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2042669 + ... + 2042708.

It is an arithmetic number, because the mean of its divisors is an integer number (14298823).

Almost surely, 2^81707540 is an apocalyptic number.

It is an amenable number.

81707540 is an abundant number, since it is smaller than the sum of its proper divisors (89878336).

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

81707540 is a wasteful number, since it uses less digits than its factorization.

81707540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4085386 (or 4085384 counting only the distinct ones).

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 81707540 is about 9039.2223116815. Note that the first 3 decimals coincide. The cubic root of 81707540 is about 433.9310345086.

The spelling of 81707540 in words is "eighty-one million, seven hundred seven thousand, five hundred forty".