81621241 has 4 divisors (see below), whose sum is σ = 87899812. Its totient is φ = 75342672.

The previous prime is 81621203. The next prime is 81621247. The reversal of 81621241 is 14212618.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 35652841 + 45968400 = 5971^2 + 6780^2 .

It is a cyclic number.

It is not a de Polignac number, because 81621241 - 2¹⁵ = 81588473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81621247) 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, 3139266 + ... + 3139291.

It is an arithmetic number, because the mean of its divisors is an integer number (21974953).

Almost surely, 2^81621241 is an apocalyptic number.

It is an amenable number.

81621241 is a deficient number, since it is larger than the sum of its proper divisors (6278571).

81621241 is a wasteful number, since it uses less digits than its factorization.

81621241 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6278570.

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

The square root of 81621241 is about 9034.4474651193. The cubic root of 81621241 is about 433.7782089304.

Adding to 81621241 its reverse (14212618), we get a palindrome (95833859).

The spelling of 81621241 in words is "eighty-one million, six hundred twenty-one thousand, two hundred forty-one".