21521212 has 6 divisors (see below), whose sum is σ = 37662128. Its totient is φ = 10760604.

The previous prime is 21521183. The next prime is 21521249. The reversal of 21521212 is 21212512.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 2690148 + ... + 2690155.

Almost surely, 2^21521212 is an apocalyptic number.

It is an amenable number.

21521212 is a deficient number, since it is larger than the sum of its proper divisors (16140916).

21521212 is a wasteful number, since it uses less digits than its factorization.

21521212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5380307 (or 5380305 counting only the distinct ones).

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

The square root of 21521212 is about 4639.0960326339. The cubic root of 21521212 is about 278.1563049727.

Adding to 21521212 its reverse (21212512), we get a palindrome (42733724).

It can be divided in two parts, 2152 and 1212, that added together give a square (3364 = 58²).

The spelling of 21521212 in words is "twenty-one million, five hundred twenty-one thousand, two hundred twelve".