21201212121 has 16 divisors (see below), whose sum is σ = 29041093248. Its totient is φ = 13747968000.

The previous prime is 21201212051. The next prime is 21201212143. The reversal of 21201212121 is 12121210212.

It is not a de Polignac number, because 21201212121 - 2⁹ = 21201211609 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21201212121.

It is not an unprimeable number, because it can be changed into a prime (21201212171) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 362521 + ... + 416921.

It is an arithmetic number, because the mean of its divisors is an integer number (1815068328).

Almost surely, 2^21201212121 is an apocalyptic number.

It is an amenable number.

21201212121 is a deficient number, since it is larger than the sum of its proper divisors (7839881127).

21201212121 is a wasteful number, since it uses less digits than its factorization.

21201212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57952.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21201212121 its reverse (12121210212), we get a palindrome (33322422333).

The spelling of 21201212121 in words is "twenty-one billion, two hundred one million, two hundred twelve thousand, one hundred twenty-one".