21507526506421 has 4 divisors (see below), whose sum is σ = 22249165351500. Its totient is φ = 20765887661344.

The previous prime is 21507526506413. The next prime is 21507526506517. The reversal of 21507526506421 is 12460562570512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15271768383921 + 6235758122500 = 3907911^2 + 2497150^2 .

It is a cyclic number.

It is not a de Polignac number, because 21507526506421 - 2³ = 21507526506413 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 (21507526536421) 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, 370819422496 + ... + 370819422553.

It is an arithmetic number, because the mean of its divisors is an integer number (5562291337875).

Almost surely, 2^{21507526506421} is an apocalyptic number.

It is an amenable number.

21507526506421 is a deficient number, since it is larger than the sum of its proper divisors (741638845079).

21507526506421 is an equidigital number, since it uses as much as digits as its factorization.

21507526506421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 741638845078.

The product of its (nonzero) digits is 1008000, while the sum is 46.

The spelling of 21507526506421 in words is "twenty-one trillion, five hundred seven billion, five hundred twenty-six million, five hundred six thousand, four hundred twenty-one".