21012212021 has 4 divisors (see below), whose sum is σ = 21690025344. Its totient is φ = 20334398700.

The previous prime is 21012212009. The next prime is 21012212069. The reversal of 21012212021 is 12021221012.

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 not a de Polignac number, because 21012212021 - 2¹⁰ = 21012210997 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21012211987 and 21012212005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012214021) 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, 338906615 + ... + 338906676.

It is an arithmetic number, because the mean of its divisors is an integer number (5422506336).

Almost surely, 2^21012212021 is an apocalyptic number.

It is an amenable number.

21012212021 is a deficient number, since it is larger than the sum of its proper divisors (677813323).

21012212021 is an equidigital number, since it uses as much as digits as its factorization.

21012212021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 677813322.

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

Adding to 21012212021 its reverse (12021221012), we get a palindrome (33033433033).

It can be divided in two parts, 2101 and 2212021, that added together give a palindrome (2214122).

The spelling of 21012212021 in words is "twenty-one billion, twelve million, two hundred twelve thousand, twenty-one".