21123523505 has 32 divisors (see below), whose sum is σ = 30713625600. Its totient is φ = 13623567552.

The previous prime is 21123523493. The next prime is 21123523507. The reversal of 21123523505 is 50532532112.

It is not a de Polignac number, because 21123523505 - 2⁸ = 21123523249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21123523507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 21827 + ... + 206696.

It is an arithmetic number, because the mean of its divisors is an integer number (959800800).

Almost surely, 2^21123523505 is an apocalyptic number.

It is an amenable number.

21123523505 is a deficient number, since it is larger than the sum of its proper divisors (9590102095).

21123523505 is a wasteful number, since it uses less digits than its factorization.

21123523505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228693.

The product of its (nonzero) digits is 9000, while the sum is 29.

The spelling of 21123523505 in words is "twenty-one billion, one hundred twenty-three million, five hundred twenty-three thousand, five hundred five".