21653733506261 has 4 divisors (see below), whose sum is σ = 21653745432012. Its totient is φ = 21653721580512.

The previous prime is 21653733506239. The next prime is 21653733506267. The reversal of 21653733506261 is 16260533735612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 21447957865636 + 205775640625 = 4631194^2 + 453625^2 .

It is a cyclic number.

It is not a de Polignac number, because 21653733506261 - 2²⁶ = 21653666397397 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 (21653733506267) 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, 2611400 + ... + 7080033.

It is an arithmetic number, because the mean of its divisors is an integer number (5413436358003).

Almost surely, 2^{21653733506261} is an apocalyptic number.

It is an amenable number.

21653733506261 is a deficient number, since it is larger than the sum of its proper divisors (11925751).

21653733506261 is an equidigital number, since it uses as much as digits as its factorization.

21653733506261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11925750.

The product of its (nonzero) digits is 4082400, while the sum is 50.

The spelling of 21653733506261 in words is "twenty-one trillion, six hundred fifty-three billion, seven hundred thirty-three million, five hundred six thousand, two hundred sixty-one".