21311523 has 12 divisors (see below), whose sum is σ = 32594328. Its totient is φ = 13371840.

The previous prime is 21311503. The next prime is 21311527. The reversal of 21311523 is 32511312.

It is not a de Polignac number, because 21311523 - 2¹⁷ = 21180451 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21311496 and 21311505.

It is not an unprimeable number, because it can be changed into a prime (21311527) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 69493 + ... + 69798.

It is an arithmetic number, because the mean of its divisors is an integer number (2716194).

Almost surely, 2^21311523 is an apocalyptic number.

21311523 is a deficient number, since it is larger than the sum of its proper divisors (11282805).

21311523 is a wasteful number, since it uses less digits than its factorization.

21311523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139314 (or 139311 counting only the distinct ones).

The product of its digits is 180, while the sum is 18.

The square root of 21311523 is about 4616.4405119096. The cubic root of 21311523 is about 277.2499622592.

Adding to 21311523 its reverse (32511312), we get a palindrome (53822835).

The spelling of 21311523 in words is "twenty-one million, three hundred eleven thousand, five hundred twenty-three".