21212786 has 24 divisors (see below), whose sum is σ = 37213020. Its totient is φ = 9042432.

The previous prime is 21212777. The next prime is 21212809. The reversal of 21212786 is 68721212.

It can be written as a sum of positive squares in 2 ways, for example, as 16654561 + 4558225 = 4081^2 + 2135^2 .

It is an unprimeable number.

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, 22370 + ... + 23298.

Almost surely, 2^21212786 is an apocalyptic number.

21212786 is a deficient number, since it is larger than the sum of its proper divisors (16000234).

21212786 is a wasteful number, since it uses less digits than its factorization.

21212786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1178 (or 1171 counting only the distinct ones).

The product of its digits is 2688, while the sum is 29.

The square root of 21212786 is about 4605.7340348744. The cubic root of 21212786 is about 276.8211298565.

Adding to 21212786 its reverse (68721212), we get a palindrome (89933998).

The spelling of 21212786 in words is "twenty-one million, two hundred twelve thousand, seven hundred eighty-six".