81421213 has 4 divisors (see below), whose sum is σ = 85706560. Its totient is φ = 77135868.

The previous prime is 81421187. The next prime is 81421217. The reversal of 81421213 is 31212418.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 81421213 - 2⁵ = 81421181 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 (81421217) 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, 2142645 + ... + 2142682.

It is an arithmetic number, because the mean of its divisors is an integer number (21426640).

Almost surely, 2^81421213 is an apocalyptic number.

It is an amenable number.

81421213 is a deficient number, since it is larger than the sum of its proper divisors (4285347).

81421213 is a wasteful number, since it uses less digits than its factorization.

81421213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4285346.

The product of its digits is 384, while the sum is 22.

The square root of 81421213 is about 9023.3703791876. The cubic root of 81421213 is about 433.4235677309.

The spelling of 81421213 in words is "eighty-one million, four hundred twenty-one thousand, two hundred thirteen".