21122021 has 4 divisors (see below), whose sum is σ = 21158592. Its totient is φ = 21085452.

The previous prime is 21122009. The next prime is 21122033. The reversal of 21122021 is 12022112.

It is a happy number.

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 an interprime number because it is at equal distance from previous prime (21122009) and next prime (21122033).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21122021 is a prime.

It is a super-2 number, since 2×21122021² = 892279542248882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121993 and 21122011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122221) 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, 17405 + ... + 18578.

It is an arithmetic number, because the mean of its divisors is an integer number (5289648).

Almost surely, 2^21122021 is an apocalyptic number.

It is an amenable number.

21122021 is a deficient number, since it is larger than the sum of its proper divisors (36571).

21122021 is an equidigital number, since it uses as much as digits as its factorization.

21122021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36570.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 21122021 is about 4595.8699938097. The cubic root of 21122021 is about 276.4257458165.

Adding to 21122021 its reverse (12022112), we get a palindrome (33144133).

Subtracting from 21122021 its reverse (12022112), we obtain a palindrome (9099909).

The spelling of 21122021 in words is "twenty-one million, one hundred twenty-two thousand, twenty-one".