21251212 has 6 divisors (see below), whose sum is σ = 37189628. Its totient is φ = 10625604.

The previous prime is 21251201. The next prime is 21251239. The reversal of 21251212 is 21215212.

It is a happy number.

It is a super-2 number, since 2×21251212² = 903228022937888, which contains 22 as substring.

It is a plaindrome in base 16.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2656398 + ... + 2656405.

Almost surely, 2^21251212 is an apocalyptic number.

It is an amenable number.

21251212 is a deficient number, since it is larger than the sum of its proper divisors (15938416).

21251212 is a wasteful number, since it uses less digits than its factorization.

21251212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5312807 (or 5312805 counting only the distinct ones).

The product of its digits is 80, while the sum is 16.

The square root of 21251212 is about 4609.9036866295. The cubic root of 21251212 is about 276.9881786716.

Adding to 21251212 its reverse (21215212), we get a palindrome (42466424).

The spelling of 21251212 in words is "twenty-one million, two hundred fifty-one thousand, two hundred twelve".