21253240034561 has 2 divisors, whose sum is σ = 21253240034562. Its totient is φ = 21253240034560.

The previous prime is 21253240034531. The next prime is 21253240034633. The reversal of 21253240034561 is 16543004235212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11647852281025 + 9605387753536 = 3412895^2 + 3099256^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253240034561 - 2¹⁴ = 21253240018177 is a prime.

It is not a weakly prime, because it can be changed into another prime (21253240034531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10626620017280 + 10626620017281.

It is an arithmetic number, because the mean of its divisors is an integer number (10626620017281).

Almost surely, 2^{21253240034561} is an apocalyptic number.

It is an amenable number.

21253240034561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21253240034561 is an equidigital number, since it uses as much as digits as its factorization.

21253240034561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 172800, while the sum is 38.

Adding to 21253240034561 its reverse (16543004235212), we get a palindrome (37796244269773).

The spelling of 21253240034561 in words is "twenty-one trillion, two hundred fifty-three billion, two hundred forty million, thirty-four thousand, five hundred sixty-one".