81461402081 has 4 divisors (see below), whose sum is σ = 82796834964. Its totient is φ = 80125969200.

The previous prime is 81461402051. The next prime is 81461402119. The reversal of 81461402081 is 18020416418.

It is a happy number.

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 32984371456 + 48477030625 = 181616^2 + 220175^2 .

It is a cyclic number.

It is not a de Polignac number, because 81461402081 - 2¹⁴ = 81461385697 is a prime.

It is a super-2 number, since 2×81461402081² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81461402051) 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, 667716350 + ... + 667716471.

It is an arithmetic number, because the mean of its divisors is an integer number (20699208741).

Almost surely, 2^81461402081 is an apocalyptic number.

It is an amenable number.

81461402081 is a deficient number, since it is larger than the sum of its proper divisors (1335432883).

81461402081 is a wasteful number, since it uses less digits than its factorization.

81461402081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1335432882.

The product of its (nonzero) digits is 12288, while the sum is 35.

Adding to 81461402081 its reverse (18020416418), we get a palindrome (99481818499).

The spelling of 81461402081 in words is "eighty-one billion, four hundred sixty-one million, four hundred two thousand, eighty-one".