21863261 has 6 divisors (see below), whose sum is σ = 25432830. Its totient is φ = 18739896.

The previous prime is 21863227. The next prime is 21863267. The reversal of 21863261 is 16236812.

It can be written as a sum of positive squares in only one way, i.e., 21215236 + 648025 = 4606^2 + 805^2 .

It is not a de Polignac number, because 21863261 - 2¹⁰ = 21862237 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 (21863267) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 223046 + ... + 223143.

It is an arithmetic number, because the mean of its divisors is an integer number (4238805).

Almost surely, 2^21863261 is an apocalyptic number.

It is an amenable number.

21863261 is a deficient number, since it is larger than the sum of its proper divisors (3569569).

21863261 is an equidigital number, since it uses as much as digits as its factorization.

21863261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 446203 (or 446196 counting only the distinct ones).

The product of its digits is 3456, while the sum is 29.

The square root of 21863261 is about 4675.8166131704. The cubic root of 21863261 is about 279.6221987992.

The spelling of 21863261 in words is "twenty-one million, eight hundred sixty-three thousand, two hundred sixty-one".