81268021 has 4 divisors (see below), whose sum is σ = 83464492. Its totient is φ = 79071552.

The previous prime is 81268003. The next prime is 81268037. The reversal of 81268021 is 12086218.

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 59505796 + 21762225 = 7714^2 + 4665^2 .

It is a cyclic number.

It is not a de Polignac number, because 81268021 - 2⁹ = 81267509 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 (81268001) 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, 1098180 + ... + 1098253.

It is an arithmetic number, because the mean of its divisors is an integer number (20866123).

Almost surely, 2^81268021 is an apocalyptic number.

It is an amenable number.

81268021 is a deficient number, since it is larger than the sum of its proper divisors (2196471).

81268021 is a wasteful number, since it uses less digits than its factorization.

81268021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2196470.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 81268021 is about 9014.8777584613. The cubic root of 81268021 is about 433.1515718314.

The spelling of 81268021 in words is "eighty-one million, two hundred sixty-eight thousand, twenty-one".