21506205474511 has 4 divisors (see below), whose sum is σ = 21506216414272. Its totient is φ = 21506194534752.

The previous prime is 21506205474469. The next prime is 21506205474527. The reversal of 21506205474511 is 11547450260512.

It is a happy number.

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 is a cyclic number.

It is not a de Polignac number, because 21506205474511 - 2²¹ = 21506203377359 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 (21506205474211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1615935 + ... + 6754528.

It is an arithmetic number, because the mean of its divisors is an integer number (5376554103568).

Almost surely, 2^{21506205474511} is an apocalyptic number.

21506205474511 is a deficient number, since it is larger than the sum of its proper divisors (10939761).

21506205474511 is an equidigital number, since it uses as much as digits as its factorization.

21506205474511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10939760.

The product of its (nonzero) digits is 336000, while the sum is 43.

The spelling of 21506205474511 in words is "twenty-one trillion, five hundred six billion, two hundred five million, four hundred seventy-four thousand, five hundred eleven".