21621211 has 8 divisors (see below), whose sum is σ = 22488480. Its totient is φ = 20762112.

The previous prime is 21621181. The next prime is 21621233. The reversal of 21621211 is 11212612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21621211 - 2⁵ = 21621179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21681211) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3666 + ... + 7528.

It is an arithmetic number, because the mean of its divisors is an integer number (2811060).

Almost surely, 2^21621211 is an apocalyptic number.

21621211 is a deficient number, since it is larger than the sum of its proper divisors (867269).

21621211 is a wasteful number, since it uses less digits than its factorization.

21621211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4085.

The product of its digits is 48, while the sum is 16.

The square root of 21621211 is about 4649.8613957837. The cubic root of 21621211 is about 278.5864601388.

Adding to 21621211 its reverse (11212612), we get a palindrome (32833823).

The spelling of 21621211 in words is "twenty-one million, six hundred twenty-one thousand, two hundred eleven".