21313509 has 16 divisors (see below), whose sum is σ = 33234432. Its totient is φ = 11895408.

The previous prime is 21313493. The next prime is 21313531. The reversal of 21313509 is 90531312.

It is a happy number.

It is not a de Polignac number, because 21313509 - 2⁴ = 21313493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313609) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10899 + ... + 12704.

It is an arithmetic number, because the mean of its divisors is an integer number (2077152).

Almost surely, 2^21313509 is an apocalyptic number.

It is an amenable number.

21313509 is a deficient number, since it is larger than the sum of its proper divisors (11920923).

21313509 is a wasteful number, since it uses less digits than its factorization.

21313509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23656.

The product of its (nonzero) digits is 810, while the sum is 24.

The square root of 21313509 is about 4616.6556076883. The cubic root of 21313509 is about 277.2585742094.

The spelling of 21313509 in words is "twenty-one million, three hundred thirteen thousand, five hundred nine".