81131687479969 has 27 divisors (see below), whose sum is σ = 97746503655411. Its totient is φ = 67141952272080.

The previous prime is 81131687479937. The next prime is 81131687480057. The reversal of 81131687479969 is 96997478613118.

The square root of 81131687479969 is 9007313.

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

It can be written as a sum of positive squares in only one way, i.e., 42543488916369 + 38588198563600 = 6522537^2 + 6211940^2 .

It is not a de Polignac number, because 81131687479969 - 2⁵ = 81131687479937 is a prime.

It is a super-2 number, since 2×81131687479969² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81131681479969) 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, 1828462354 + ... + 1828506724.

Almost surely, 2^{81131687479969} is an apocalyptic number.

81131687479969 is the 9007313-rd square number.

81131687479969 is the 4503657-th centered octagonal number.

It is an amenable number.

81131687479969 is a deficient number, since it is larger than the sum of its proper divisors (16614816175442).

81131687479969 is an frugal number, since it uses more digits than its factorization.

81131687479969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88814 (or 44407 counting only the distinct ones).

The product of its digits is 987614208, while the sum is 79.

The spelling of 81131687479969 in words is "eighty-one trillion, one hundred thirty-one billion, six hundred eighty-seven million, four hundred seventy-nine thousand, nine hundred sixty-nine".