81209610729 has 27 divisors (see below), whose sum is σ = 127037546103. Its totient is φ = 49968305712.

The previous prime is 81209610721. The next prime is 81209610737. The reversal of 81209610729 is 92701690218.

The square root of 81209610729 is 284973.

It is a perfect power (a square), and thus also a powerful number.

81209610729 is a `hidden beast` number, since 8 + 1 + 2 + 0 + 9 + 610 + 7 + 29 = 666.

It is an interprime number because it is at equal distance from previous prime (81209610721) and next prime (81209610737).

It can be written as a sum of positive squares in only one way, i.e., 12013256025 + 69196354704 = 109605^2 + 263052^2 .

It is not a de Polignac number, because 81209610729 - 2³ = 81209610721 is a prime.

It is a super-2 number, since 2×81209610729² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81209610721) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 11110294 + ... + 11117600.

Almost surely, 2^81209610729 is an apocalyptic number.

81209610729 is the 284973-rd square number.

81209610729 is the 142487-th centered octagonal number.

It is an amenable number.

81209610729 is a deficient number, since it is larger than the sum of its proper divisors (45827935374).

81209610729 is an frugal number, since it uses more digits than its factorization.

81209610729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14646 (or 7323 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The spelling of 81209610729 in words is "eighty-one billion, two hundred nine million, six hundred ten thousand, seven hundred twenty-nine".