81461821 has 4 divisors (see below), whose sum is σ = 93099232. Its totient is φ = 69824412.

The previous prime is 81461819. The next prime is 81461839. The reversal of 81461821 is 12816418.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12816418 = 2 ⋅6408209.

It is not a de Polignac number, because 81461821 - 2¹ = 81461819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81461801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5818695 + ... + 5818708.

It is an arithmetic number, because the mean of its divisors is an integer number (23274808).

Almost surely, 2^81461821 is an apocalyptic number.

It is an amenable number.

81461821 is a deficient number, since it is larger than the sum of its proper divisors (11637411).

81461821 is a wasteful number, since it uses less digits than its factorization.

81461821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11637410.

The product of its digits is 3072, while the sum is 31.

The square root of 81461821 is about 9025.6202556943. The cubic root of 81461821 is about 433.4956109507.

The spelling of 81461821 in words is "eighty-one million, four hundred sixty-one thousand, eight hundred twenty-one".