21987449 has 8 divisors (see below), whose sum is σ = 24025248. Its totient is φ = 19956160.

The previous prime is 21987403. The next prime is 21987461. The reversal of 21987449 is 94478912.

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 21987449 - 2²⁰ = 20938873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21987479) 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, 7889 + ... + 10305.

It is an arithmetic number, because the mean of its divisors is an integer number (3003156).

Almost surely, 2^21987449 is an apocalyptic number.

It is an amenable number.

21987449 is a deficient number, since it is larger than the sum of its proper divisors (2037799).

21987449 is a wasteful number, since it uses less digits than its factorization.

21987449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3255.

The product of its digits is 145152, while the sum is 44.

The square root of 21987449 is about 4689.0776278496. The cubic root of 21987449 is about 280.1506374813.

The spelling of 21987449 in words is "twenty-one million, nine hundred eighty-seven thousand, four hundred forty-nine".