21212001 has 12 divisors (see below), whose sum is σ = 30927312. Its totient is φ = 14008536.

The previous prime is 21211997. The next prime is 21212017. The reversal of 21212001 is 10021212.

It is not a de Polignac number, because 21212001 - 2² = 21211997 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21212071) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10051 + ... + 11976.

It is an arithmetic number, because the mean of its divisors is an integer number (2577276).

Almost surely, 2^21212001 is an apocalyptic number.

It is an amenable number.

21212001 is a deficient number, since it is larger than the sum of its proper divisors (9715311).

21212001 is a wasteful number, since it uses less digits than its factorization.

21212001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22140 (or 22137 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21212001 is about 4605.6488142280. The cubic root of 21212001 is about 276.8177151350.

Adding to 21212001 its reverse (10021212), we get a palindrome (31233213).

The spelling of 21212001 in words is "twenty-one million, two hundred twelve thousand, one".