21405126013 has 2 divisors, whose sum is σ = 21405126014. Its totient is φ = 21405126012.

The previous prime is 21405125983. The next prime is 21405126121. The reversal of 21405126013 is 31062150412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18457396164 + 2947729849 = 135858^2 + 54293^2 .

It is a cyclic number.

It is not a de Polignac number, because 21405126013 - 2⁵ = 21405125981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405126313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702563006 + 10702563007.

It is an arithmetic number, because the mean of its divisors is an integer number (10702563007).

Almost surely, 2^21405126013 is an apocalyptic number.

It is an amenable number.

21405126013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405126013 is an equidigital number, since it uses as much as digits as its factorization.

21405126013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 25.

Adding to 21405126013 its reverse (31062150412), we get a palindrome (52467276425).

The spelling of 21405126013 in words is "twenty-one billion, four hundred five million, one hundred twenty-six thousand, thirteen".