21626261 has 4 divisors (see below), whose sum is σ = 22898412. Its totient is φ = 20354112.

The previous prime is 21626219. The next prime is 21626281. The reversal of 21626261 is 16262612.

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 7980625 + 13645636 = 2825^2 + 3694^2 .

It is a cyclic number.

It is not a de Polignac number, because 21626261 - 2⁶ = 21626197 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21626261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21626201) 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, 636050 + ... + 636083.

It is an arithmetic number, because the mean of its divisors is an integer number (5724603).

Almost surely, 2^21626261 is an apocalyptic number.

It is an amenable number.

21626261 is a deficient number, since it is larger than the sum of its proper divisors (1272151).

21626261 is a wasteful number, since it uses less digits than its factorization.

21626261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1272150.

The product of its digits is 1728, while the sum is 26.

The square root of 21626261 is about 4650.4043910181. The cubic root of 21626261 is about 278.6081479789.

Adding to 21626261 its reverse (16262612), we get a palindrome (37888873).

The spelling of 21626261 in words is "twenty-one million, six hundred twenty-six thousand, two hundred sixty-one".