21395509 has 8 divisors (see below), whose sum is σ = 22052768. Its totient is φ = 20742480.

The previous prime is 21395477. The next prime is 21395513. The reversal of 21395509 is 90559312.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21395509 - 2⁵ = 21395477 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 (21395599) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11374 + ... + 13120.

It is an arithmetic number, because the mean of its divisors is an integer number (2756596).

Almost surely, 2^21395509 is an apocalyptic number.

It is an amenable number.

21395509 is a deficient number, since it is larger than the sum of its proper divisors (657259).

21395509 is a wasteful number, since it uses less digits than its factorization.

21395509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2115.

The product of its (nonzero) digits is 12150, while the sum is 34.

The square root of 21395509 is about 4625.5279698646. The cubic root of 21395509 is about 277.6136871516.

It can be divided in two parts, 21395 and 509, that added together give a square (21904 = 148²).

The spelling of 21395509 in words is "twenty-one million, three hundred ninety-five thousand, five hundred nine".