21025913 has 4 divisors (see below), whose sum is σ = 22132560. Its totient is φ = 19919268.

The previous prime is 21025909. The next prime is 21025937. The reversal of 21025913 is 31952012.

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 21025913 - 2² = 21025909 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21025313) 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, 553295 + ... + 553332.

It is an arithmetic number, because the mean of its divisors is an integer number (5533140).

Almost surely, 2^21025913 is an apocalyptic number.

It is an amenable number.

21025913 is a deficient number, since it is larger than the sum of its proper divisors (1106647).

21025913 is a wasteful number, since it uses less digits than its factorization.

21025913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1106646.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21025913 is about 4585.4021633876. The cubic root of 21025913 is about 276.0058503626.

Adding to 21025913 its reverse (31952012), we get a palindrome (52977925).

The spelling of 21025913 in words is "twenty-one million, twenty-five thousand, nine hundred thirteen".