21321261 has 12 divisors (see below), whose sum is σ = 33166588. Its totient is φ = 13120704.

The previous prime is 21321217. The next prime is 21321263. The reversal of 21321261 is 16212312.

21321261 = T₁₅₈ + T₁₅₉ + ... + T₅₀₈.

It can be written as a sum of positive squares in 2 ways, for example, as 9418761 + 11902500 = 3069^2 + 3450^2 .

It is not a de Polignac number, because 21321261 - 2⁶ = 21321197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321263) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 91000 + ... + 91233.

Almost surely, 2^21321261 is an apocalyptic number.

It is an amenable number.

21321261 is a deficient number, since it is larger than the sum of its proper divisors (11845327).

21321261 is a wasteful number, since it uses less digits than its factorization.

21321261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182252 (or 182249 counting only the distinct ones).

The product of its digits is 144, while the sum is 18.

The square root of 21321261 is about 4617.4951001598. The cubic root of 21321261 is about 277.2921843162.

Adding to 21321261 its reverse (16212312), we get a palindrome (37533573).

The spelling of 21321261 in words is "twenty-one million, three hundred twenty-one thousand, two hundred sixty-one".