81678421 has 16 divisors (see below), whose sum is σ = 94678848. Its totient is φ = 69638400.

The previous prime is 81678407. The next prime is 81678431. The reversal of 81678421 is 12487618.

It is a cyclic number.

It is not a de Polignac number, because 81678421 - 2⁹ = 81677909 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81678431) 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 15 ways as a sum of consecutive naturals, for example, 69166 + ... + 70336.

It is an arithmetic number, because the mean of its divisors is an integer number (5917428).

Almost surely, 2^81678421 is an apocalyptic number.

It is an amenable number.

81678421 is a deficient number, since it is larger than the sum of its proper divisors (13000427).

81678421 is a wasteful number, since it uses less digits than its factorization.

81678421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1572.

The product of its digits is 21504, while the sum is 37.

The square root of 81678421 is about 9037.6114654260. The cubic root of 81678421 is about 433.8794801513.

The spelling of 81678421 in words is "eighty-one million, six hundred seventy-eight thousand, four hundred twenty-one".