81946421 has 4 divisors (see below), whose sum is σ = 82029612. Its totient is φ = 81863232.

The previous prime is 81946393. The next prime is 81946429. The reversal of 81946421 is 12464918.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12464918 = 2 ⋅6232459.

It can be written as a sum of positive squares in 2 ways, for example, as 29311396 + 52635025 = 5414^2 + 7255^2 .

It is a cyclic number.

It is not a de Polignac number, because 81946421 - 2²² = 77752117 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 (81946429) 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, 40100 + ... + 42093.

It is an arithmetic number, because the mean of its divisors is an integer number (20507403).

Almost surely, 2^81946421 is an apocalyptic number.

It is an amenable number.

81946421 is a deficient number, since it is larger than the sum of its proper divisors (83191).

81946421 is an equidigital number, since it uses as much as digits as its factorization.

81946421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83190.

The product of its digits is 13824, while the sum is 35.

The square root of 81946421 is about 9052.4262493544. The cubic root of 81946421 is about 434.3535048004.

The spelling of 81946421 in words is "eighty-one million, nine hundred forty-six thousand, four hundred twenty-one".