21022221 has 16 divisors (see below), whose sum is σ = 30804480. Its totient is φ = 12646320.

The previous prime is 21022219. The next prime is 21022223. The reversal of 21022221 is 12222012.

It is an interprime number because it is at equal distance from previous prime (21022219) and next prime (21022223).

It is not a de Polignac number, because 21022221 - 2¹ = 21022219 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21022197 and 21022206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21022223) 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, 2296 + ... + 6878.

It is an arithmetic number, because the mean of its divisors is an integer number (1925280).

Almost surely, 2^21022221 is an apocalyptic number.

It is an amenable number.

21022221 is a deficient number, since it is larger than the sum of its proper divisors (9782259).

21022221 is a wasteful number, since it uses less digits than its factorization.

21022221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4736.

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 21022221 is about 4584.9995637950. Note that the first 3 decimals coincide. The cubic root of 21022221 is about 275.9896945322.

Adding to 21022221 its reverse (12222012), we get a palindrome (33244233).

The spelling of 21022221 in words is "twenty-one million, twenty-two thousand, two hundred twenty-one".