81921427 has 4 divisors (see below), whose sum is σ = 93624496. Its totient is φ = 70218360.

The previous prime is 81921421. The next prime is 81921431. The reversal of 81921427 is 72412918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 72412918 = 2 ⋅36206459.

It is a cyclic number.

It is not a de Polignac number, because 81921427 - 2⁷ = 81921299 is a prime.

It is a super-2 number, since 2×81921427² = 13422240403432658, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81921392 and 81921401.

It is not an unprimeable number, because it can be changed into a prime (81921421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5851524 + ... + 5851537.

It is an arithmetic number, because the mean of its divisors is an integer number (23406124).

Almost surely, 2^81921427 is an apocalyptic number.

81921427 is a deficient number, since it is larger than the sum of its proper divisors (11703069).

81921427 is a wasteful number, since it uses less digits than its factorization.

81921427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11703068.

The product of its digits is 8064, while the sum is 34.

The square root of 81921427 is about 9051.0456302021. The cubic root of 81921427 is about 434.3093404335.

The spelling of 81921427 in words is "eighty-one million, nine hundred twenty-one thousand, four hundred twenty-seven".