81226021 has 4 divisors (see below), whose sum is σ = 81367372. Its totient is φ = 81084672.

The previous prime is 81226003. The next prime is 81226031. The reversal of 81226021 is 12062218.

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 76212900 + 5013121 = 8730^2 + 2239^2 .

It is a cyclic number.

It is not a de Polignac number, because 81226021 - 2²¹ = 79128869 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81225983 and 81226001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81226001) 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, 69810 + ... + 70963.

It is an arithmetic number, because the mean of its divisors is an integer number (20341843).

Almost surely, 2^81226021 is an apocalyptic number.

It is an amenable number.

81226021 is a deficient number, since it is larger than the sum of its proper divisors (141351).

81226021 is a wasteful number, since it uses less digits than its factorization.

81226021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141350.

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

The square root of 81226021 is about 9012.5479749070. The cubic root of 81226021 is about 433.0769401756.

Adding to 81226021 its reverse (12062218), we get a palindrome (93288239).

The spelling of 81226021 in words is "eighty-one million, two hundred twenty-six thousand, twenty-one".