21211621 has 8 divisors (see below), whose sum is σ = 21677760. Its totient is φ = 20749152.

The previous prime is 21211613. The next prime is 21211643. The reversal of 21211621 is 12611212.

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 21211621 - 2³ = 21211613 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21211595 and 21211604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12976 + ... + 14518.

It is an arithmetic number, because the mean of its divisors is an integer number (2709720).

Almost surely, 2^21211621 is an apocalyptic number.

It is an amenable number.

21211621 is a deficient number, since it is larger than the sum of its proper divisors (466139).

21211621 is a wasteful number, since it uses less digits than its factorization.

21211621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1835.

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

The square root of 21211621 is about 4605.6075603551. The cubic root of 21211621 is about 276.8160621185.

Adding to 21211621 its reverse (12611212), we get a palindrome (33822833).

It can be divided in two parts, 2 and 1211621, that multiplied together give a palindrome (2423242).

The spelling of 21211621 in words is "twenty-one million, two hundred eleven thousand, six hundred twenty-one".