21323212021 has 4 divisors (see below), whose sum is σ = 21325862700. Its totient is φ = 21320561344.

The previous prime is 21323212003. The next prime is 21323212039. The reversal of 21323212021 is 12021232312.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21323212003) and next prime (21323212039).

It can be written as a sum of positive squares in 2 ways, for example, as 554367025 + 20768844996 = 23545^2 + 144114^2 .

It is a cyclic number.

It is not a de Polignac number, because 21323212021 - 2⁷ = 21323211893 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21323212021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21323212051) 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, 1313236 + ... + 1329373.

It is an arithmetic number, because the mean of its divisors is an integer number (5331465675).

Almost surely, 2^21323212021 is an apocalyptic number.

It is an amenable number.

21323212021 is a deficient number, since it is larger than the sum of its proper divisors (2650679).

21323212021 is an equidigital number, since it uses as much as digits as its factorization.

21323212021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2650678.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21323212021 its reverse (12021232312), we get a palindrome (33344444333).

The spelling of 21323212021 in words is "twenty-one billion, three hundred twenty-three million, two hundred twelve thousand, twenty-one".