21222001 has 4 divisors (see below), whose sum is σ = 22470372. Its totient is φ = 19973632.

The previous prime is 21221953. The next prime is 21222013. The reversal of 21222001 is 10022212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 17438976 + 3783025 = 4176^2 + 1945^2 .

It is a cyclic number.

It is not a de Polignac number, because 21222001 - 2¹³ = 21213809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21222041) 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, 624160 + ... + 624193.

It is an arithmetic number, because the mean of its divisors is an integer number (5617593).

Almost surely, 2^21222001 is an apocalyptic number.

It is an amenable number.

21222001 is a deficient number, since it is larger than the sum of its proper divisors (1248371).

21222001 is a wasteful number, since it uses less digits than its factorization.

21222001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1248370.

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21222001 is about 4606.7343096819. The cubic root of 21222001 is about 276.8612084742.

Adding to 21222001 its reverse (10022212), we get a palindrome (31244213).

The spelling of 21222001 in words is "twenty-one million, two hundred twenty-two thousand, one".