21212737 has 12 divisors (see below), whose sum is σ = 26574996. Its totient is φ = 16783200.

The previous prime is 21212731. The next prime is 21212749. The reversal of 21212737 is 73721212.

It can be written as a sum of positive squares in 2 ways, for example, as 8317456 + 12895281 = 2884^2 + 3591^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21212737 is a prime.

It is a super-2 number, since 2×21212737² = 899960422062338, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21212731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16014 + ... + 17287.

It is an arithmetic number, because the mean of its divisors is an integer number (2214583).

Almost surely, 2^21212737 is an apocalyptic number.

It is an amenable number.

21212737 is a deficient number, since it is larger than the sum of its proper divisors (5362259).

21212737 is a wasteful number, since it uses less digits than its factorization.

21212737 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33328 (or 33321 counting only the distinct ones).

The product of its digits is 1176, while the sum is 25.

The square root of 21212737 is about 4605.7287154152. The cubic root of 21212737 is about 276.8209167107.

Adding to 21212737 its reverse (73721212), we get a palindrome (94933949).

The spelling of 21212737 in words is "twenty-one million, two hundred twelve thousand, seven hundred thirty-seven".