21111621 has 4 divisors (see below), whose sum is σ = 28148832. Its totient is φ = 14074412.

The previous prime is 21111617. The next prime is 21111683. The reversal of 21111621 is 12611112.

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 a cyclic number.

It is not a de Polignac number, because 21111621 - 2² = 21111617 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21111621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111611) 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, 3518601 + ... + 3518606.

It is an arithmetic number, because the mean of its divisors is an integer number (7037208).

Almost surely, 2^21111621 is an apocalyptic number.

It is an amenable number.

21111621 is a deficient number, since it is larger than the sum of its proper divisors (7037211).

21111621 is an equidigital number, since it uses as much as digits as its factorization.

21111621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7037210.

The product of its digits is 24, while the sum is 15.

The square root of 21111621 is about 4594.7384038702. The cubic root of 21111621 is about 276.3803697969.

Adding to 21111621 its reverse (12611112), we get a palindrome (33722733).

The spelling of 21111621 in words is "twenty-one million, one hundred eleven thousand, six hundred twenty-one".