21145913 has 4 divisors (see below), whose sum is σ = 21157968. Its totient is φ = 21133860.

The previous prime is 21145871. The next prime is 21145919. The reversal of 21145913 is 31954112.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21145913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21145919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2831 + ... + 7092.

It is an arithmetic number, because the mean of its divisors is an integer number (5289492).

Almost surely, 2^21145913 is an apocalyptic number.

It is an amenable number.

21145913 is a deficient number, since it is larger than the sum of its proper divisors (12055).

21145913 is an equidigital number, since it uses as much as digits as its factorization.

21145913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12054.

The product of its digits is 1080, while the sum is 26.

The square root of 21145913 is about 4598.4685494195. The cubic root of 21145913 is about 276.5299321114.

The spelling of 21145913 in words is "twenty-one million, one hundred forty-five thousand, nine hundred thirteen".