21893509 has 4 divisors (see below), whose sum is σ = 23883840. Its totient is φ = 19903180.

The previous prime is 21893483. The next prime is 21893513. The reversal of 21893509 is 90539812.

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 not a de Polignac number, because 21893509 - 2⁵ = 21893477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21893009) 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, 995149 + ... + 995170.

It is an arithmetic number, because the mean of its divisors is an integer number (5970960).

Almost surely, 2^21893509 is an apocalyptic number.

It is an amenable number.

21893509 is a deficient number, since it is larger than the sum of its proper divisors (1990331).

21893509 is a wasteful number, since it uses less digits than its factorization.

21893509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1990330.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 21893509 is about 4679.0500104188. The cubic root of 21893509 is about 279.7510925736.

The spelling of 21893509 in words is "twenty-one million, eight hundred ninety-three thousand, five hundred nine".