21272621 has 2 divisors, whose sum is σ = 21272622. Its totient is φ = 21272620.

The previous prime is 21272617. The next prime is 21272681. The reversal of 21272621 is 12627212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17547721 + 3724900 = 4189^2 + 1930^2 .

It is a cyclic number.

It is not a de Polignac number, because 21272621 - 2² = 21272617 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21272611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10636310 + 10636311.

It is an arithmetic number, because the mean of its divisors is an integer number (10636311).

Almost surely, 2^21272621 is an apocalyptic number.

It is an amenable number.

21272621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21272621 is an equidigital number, since it uses as much as digits as its factorization.

21272621 is an evil number, because the sum of its binary digits is even.

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

The square root of 21272621 is about 4612.2251679639. The cubic root of 21272621 is about 277.0811623827.

Adding to 21272621 its reverse (12627212), we get a palindrome (33899833).

The spelling of 21272621 in words is "twenty-one million, two hundred seventy-two thousand, six hundred twenty-one".