21212775 has 36 divisors (see below), whose sum is σ = 39316680. Its totient is φ = 10920000.

The previous prime is 21212749. The next prime is 21212777. The reversal of 21212775 is 57721212.

It is not a de Polignac number, because 21212775 - 2⁸ = 21212519 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212777) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 4900 + ... + 8150.

It is an arithmetic number, because the mean of its divisors is an integer number (1092130).

Almost surely, 2^21212775 is an apocalyptic number.

21212775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21212775 is a deficient number, since it is larger than the sum of its proper divisors (18103905).

21212775 is a wasteful number, since it uses less digits than its factorization.

21212775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3296 (or 3288 counting only the distinct ones).

The product of its digits is 1960, while the sum is 27.

The square root of 21212775 is about 4605.7328407106. The cubic root of 21212775 is about 276.8210820074.

Adding to 21212775 its reverse (57721212), we get a palindrome (78933987).

The spelling of 21212775 in words is "twenty-one million, two hundred twelve thousand, seven hundred seventy-five".