21523013 has 4 divisors (see below), whose sum is σ = 21844320. Its totient is φ = 21201708.

The previous prime is 21523001. The next prime is 21523049. The reversal of 21523013 is 31032512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21523013 - 2¹⁴ = 21506629 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21522982 and 21523000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523063) 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, 160553 + ... + 160686.

It is an arithmetic number, because the mean of its divisors is an integer number (5461080).

Almost surely, 2^21523013 is an apocalyptic number.

It is an amenable number.

21523013 is a deficient number, since it is larger than the sum of its proper divisors (321307).

21523013 is an equidigital number, since it uses as much as digits as its factorization.

21523013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321306.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21523013 is about 4639.2901396658. The cubic root of 21523013 is about 278.1640639151.

Adding to 21523013 its reverse (31032512), we get a palindrome (52555525).

The spelling of 21523013 in words is "twenty-one million, five hundred twenty-three thousand, thirteen".