21227621 has 4 divisors (see below), whose sum is σ = 21264012. Its totient is φ = 21191232.

The previous prime is 21227599. The next prime is 21227629. The reversal of 21227621 is 12672212.

It is a happy number.

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 6558721 + 14668900 = 2561^2 + 3830^2 .

It is a cyclic number.

It is not a de Polignac number, because 21227621 - 2¹⁴ = 21211237 is a prime.

It is a super-2 number, since 2×21227621² = 901223786639282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21227629) 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, 17306 + ... + 18491.

It is an arithmetic number, because the mean of its divisors is an integer number (5316003).

Almost surely, 2^21227621 is an apocalyptic number.

It is an amenable number.

21227621 is a deficient number, since it is larger than the sum of its proper divisors (36391).

21227621 is an equidigital number, since it uses as much as digits as its factorization.

21227621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36390.

The product of its digits is 672, while the sum is 23.

The square root of 21227621 is about 4607.3442458753. The cubic root of 21227621 is about 276.8856457341.

Adding to 21227621 its reverse (12672212), we get a palindrome (33899833).

The spelling of 21227621 in words is "twenty-one million, two hundred twenty-seven thousand, six hundred twenty-one".