21075913 has 4 divisors (see below), whose sum is σ = 21269380. Its totient is φ = 20882448.

The previous prime is 21075907. The next prime is 21075917. The reversal of 21075913 is 31957012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15468489 + 5607424 = 3933^2 + 2368^2 .

It is a cyclic number.

It is not a de Polignac number, because 21075913 - 2⁹ = 21075401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21075917) 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, 96570 + ... + 96787.

It is an arithmetic number, because the mean of its divisors is an integer number (5317345).

Almost surely, 2^21075913 is an apocalyptic number.

It is an amenable number.

21075913 is a deficient number, since it is larger than the sum of its proper divisors (193467).

21075913 is a wasteful number, since it uses less digits than its factorization.

21075913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193466.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21075913 is about 4590.8510104337. The cubic root of 21075913 is about 276.2244594638.

The spelling of 21075913 in words is "twenty-one million, seventy-five thousand, nine hundred thirteen".