21387009 has 8 divisors (see below), whose sum is σ = 32589760. Its totient is φ = 12221136.

The previous prime is 21387001. The next prime is 21387059. The reversal of 21387009 is 90078312.

It is a happy number.

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

It is not a de Polignac number, because 21387009 - 2³ = 21387001 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21387001) 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, 509194 + ... + 509235.

It is an arithmetic number, because the mean of its divisors is an integer number (4073720).

Almost surely, 2^21387009 is an apocalyptic number.

It is an amenable number.

21387009 is a deficient number, since it is larger than the sum of its proper divisors (11202751).

21387009 is a wasteful number, since it uses less digits than its factorization.

21387009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1018439.

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 21387009 is about 4624.6090645589. The cubic root of 21387009 is about 277.5769188607.

The spelling of 21387009 in words is "twenty-one million, three hundred eighty-seven thousand, nine".