21461221 has 4 divisors (see below), whose sum is σ = 22041292. Its totient is φ = 20881152.

The previous prime is 21461213. The next prime is 21461233. The reversal of 21461221 is 12216412.

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 17892900 + 3568321 = 4230^2 + 1889^2 .

It is a cyclic number.

It is not a de Polignac number, because 21461221 - 2³ = 21461213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21461201) 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, 289980 + ... + 290053.

It is an arithmetic number, because the mean of its divisors is an integer number (5510323).

Almost surely, 2^21461221 is an apocalyptic number.

It is an amenable number.

21461221 is a deficient number, since it is larger than the sum of its proper divisors (580071).

21461221 is an equidigital number, since it uses as much as digits as its factorization.

21461221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 580070.

The product of its digits is 192, while the sum is 19.

The square root of 21461221 is about 4632.6257133509. The cubic root of 21461221 is about 277.8976082042.

Adding to 21461221 its reverse (12216412), we get a palindrome (33677633).

The spelling of 21461221 in words is "twenty-one million, four hundred sixty-one thousand, two hundred twenty-one".