81380221 has 4 divisors (see below), whose sum is σ = 87640252. Its totient is φ = 75120192.

The previous prime is 81380153. The next prime is 81380251. The reversal of 81380221 is 12208318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12208318 = 2 ⋅6104159.

It can be written as a sum of positive squares in 2 ways, for example, as 17556100 + 63824121 = 4190^2 + 7989^2 .

It is a cyclic number.

It is not a de Polignac number, because 81380221 - 2⁷ = 81380093 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 (81380251) 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, 3129996 + ... + 3130021.

It is an arithmetic number, because the mean of its divisors is an integer number (21910063).

Almost surely, 2^81380221 is an apocalyptic number.

It is an amenable number.

81380221 is a deficient number, since it is larger than the sum of its proper divisors (6260031).

81380221 is a wasteful number, since it uses less digits than its factorization.

81380221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6260030.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 81380221 is about 9021.0986581458. The cubic root of 81380221 is about 433.3508189525.

Adding to 81380221 its reverse (12208318), we get a palindrome (93588539).

The spelling of 81380221 in words is "eighty-one million, three hundred eighty thousand, two hundred twenty-one".