81539401 has 4 divisors (see below), whose sum is σ = 81562500. Its totient is φ = 81516304.

The previous prime is 81539399. The next prime is 81539411. The reversal of 81539401 is 10493518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 21631801 + 59907600 = 4651^2 + 7740^2 .

It is a cyclic number.

It is not a de Polignac number, because 81539401 - 2¹ = 81539399 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81539411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5026 + ... + 13723.

It is an arithmetic number, because the mean of its divisors is an integer number (20390625).

Almost surely, 2^81539401 is an apocalyptic number.

It is an amenable number.

81539401 is a deficient number, since it is larger than the sum of its proper divisors (23099).

81539401 is a wasteful number, since it uses less digits than its factorization.

81539401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23098.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 81539401 is about 9029.9169985111. The cubic root of 81539401 is about 433.6331801773.

The spelling of 81539401 in words is "eighty-one million, five hundred thirty-nine thousand, four hundred one".