21213631261 has 2 divisors, whose sum is σ = 21213631262. Its totient is φ = 21213631260.

The previous prime is 21213631247. The next prime is 21213631303. The reversal of 21213631261 is 16213631212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17195339161 + 4018292100 = 131131^2 + 63390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213631261 - 2⁷ = 21213631133 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21213631861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606815630 + 10606815631.

It is an arithmetic number, because the mean of its divisors is an integer number (10606815631).

Almost surely, 2^21213631261 is an apocalyptic number.

It is an amenable number.

21213631261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213631261 is an equidigital number, since it uses as much as digits as its factorization.

21213631261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 28.

The spelling of 21213631261 in words is "twenty-one billion, two hundred thirteen million, six hundred thirty-one thousand, two hundred sixty-one".