21212073 has 12 divisors (see below), whose sum is σ = 32442228. Its totient is φ = 13309440.

The previous prime is 21212071. The next prime is 21212077. The reversal of 21212073 is 37021212.

It can be written as a sum of positive squares in 2 ways, for example, as 9018009 + 12194064 = 3003^2 + 3492^2 .

It is not a de Polignac number, because 21212073 - 2¹ = 21212071 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21212071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 69168 + ... + 69473.

It is an arithmetic number, because the mean of its divisors is an integer number (2703519).

Almost surely, 2^21212073 is an apocalyptic number.

It is an amenable number.

21212073 is a deficient number, since it is larger than the sum of its proper divisors (11230155).

21212073 is a wasteful number, since it uses less digits than its factorization.

21212073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138664 (or 138661 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21212073 is about 4605.6566307097. The cubic root of 21212073 is about 276.8180283359.

Adding to 21212073 its reverse (37021212), we get a palindrome (58233285).

The spelling of 21212073 in words is "twenty-one million, two hundred twelve thousand, seventy-three".