21836621 has 4 divisors (see below), whose sum is σ = 21970752. Its totient is φ = 21702492.

The previous prime is 21836611. The next prime is 21836629. The reversal of 21836621 is 12663812.

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 21836621 - 2⁶ = 21836557 is a prime.

It is a super-3 number, since 3×21836621³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21836629) 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 3 ways as a sum of consecutive naturals, for example, 66821 + ... + 67146.

It is an arithmetic number, because the mean of its divisors is an integer number (5492688).

Almost surely, 2^21836621 is an apocalyptic number.

It is an amenable number.

21836621 is a deficient number, since it is larger than the sum of its proper divisors (134131).

21836621 is a wasteful number, since it uses less digits than its factorization.

21836621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134130.

The product of its digits is 3456, while the sum is 29.

The square root of 21836621 is about 4672.9670446088. The cubic root of 21836621 is about 279.5085810583.

The spelling of 21836621 in words is "twenty-one million, eight hundred thirty-six thousand, six hundred twenty-one".