21130621 has 4 divisors (see below), whose sum is σ = 21646044. Its totient is φ = 20615200.

The previous prime is 21130619. The next prime is 21130649. The reversal of 21130621 is 12603112.

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 1726596 + 19404025 = 1314^2 + 4405^2 .

It is a cyclic number.

It is not a de Polignac number, because 21130621 - 2¹ = 21130619 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21130595 and 21130604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21130601) 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, 257650 + ... + 257731.

It is an arithmetic number, because the mean of its divisors is an integer number (5411511).

Almost surely, 2^21130621 is an apocalyptic number.

It is an amenable number.

21130621 is a deficient number, since it is larger than the sum of its proper divisors (515423).

21130621 is an equidigital number, since it uses as much as digits as its factorization.

21130621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515422.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21130621 is about 4596.8055212288. The cubic root of 21130621 is about 276.4632570447.

Adding to 21130621 its reverse (12603112), we get a palindrome (33733733).

The spelling of 21130621 in words is "twenty-one million, one hundred thirty thousand, six hundred twenty-one".