81278421 has 8 divisors (see below), whose sum is σ = 123852864. Its totient is φ = 46444800.

The previous prime is 81278383. The next prime is 81278423. The reversal of 81278421 is 12487218.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81278421 - 2⁷ = 81278293 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81278423) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1935180 + ... + 1935221.

It is an arithmetic number, because the mean of its divisors is an integer number (15481608).

Almost surely, 2^81278421 is an apocalyptic number.

It is an amenable number.

81278421 is a deficient number, since it is larger than the sum of its proper divisors (42574443).

81278421 is a wasteful number, since it uses less digits than its factorization.

81278421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3870411.

The product of its digits is 7168, while the sum is 33.

The square root of 81278421 is about 9015.4545642469. The cubic root of 81278421 is about 433.1700480788.

The spelling of 81278421 in words is "eighty-one million, two hundred seventy-eight thousand, four hundred twenty-one".