81538231401 has 81 divisors (see below), whose sum is σ = 137791681573. Its totient is φ = 46418845440.

The previous prime is 81538231393. The next prime is 81538231409. The reversal of 81538231401 is 10413283518.

The square root of 81538231401 is 285549.

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

81538231401 is a `hidden beast` number, since 8 + 15 + 3 + 8 + 231 + 401 = 666.

It is an interprime number because it is at equal distance from previous prime (81538231393) and next prime (81538231409).

It can be written as a sum of positive squares in 4 ways, for example, as 28603265625 + 52934965776 = 169125^2 + 230076^2 .

It is not a de Polignac number, because 81538231401 - 2³ = 81538231393 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81538231409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 160192735 + ... + 160193243.

Almost surely, 2^81538231401 is an apocalyptic number.

81538231401 is the 285549-th square number.

81538231401 is the 142775-th centered octagonal number.

It is an amenable number.

81538231401 is a deficient number, since it is larger than the sum of its proper divisors (56253450172).

81538231401 is a wasteful number, since it uses less digits than its factorization.

81538231401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1080 (or 540 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

Multiplying 81538231401 by its sum of digits (36), we get a square (2935376330436 = 1713294²).

The spelling of 81538231401 in words is "eighty-one billion, five hundred thirty-eight million, two hundred thirty-one thousand, four hundred one".