21211202021 has 4 divisors (see below), whose sum is σ = 21212641344. Its totient is φ = 21209762700.

The previous prime is 21211201987. The next prime is 21211202099. The reversal of 21211202021 is 12020211212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211202021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21211201987 and 21211202005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211202521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 697325 + ... + 727106.

It is an arithmetic number, because the mean of its divisors is an integer number (5303160336).

Almost surely, 2^21211202021 is an apocalyptic number.

It is an amenable number.

21211202021 is a deficient number, since it is larger than the sum of its proper divisors (1439323).

21211202021 is a wasteful number, since it uses less digits than its factorization.

21211202021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1439322.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21211202021 its reverse (12020211212), we get a palindrome (33231413233).

The spelling of 21211202021 in words is "twenty-one billion, two hundred eleven million, two hundred two thousand, twenty-one".