21244487 has 4 divisors (see below), whose sum is σ = 23175816. Its totient is φ = 19313160.

The previous prime is 21244481. The next prime is 21244507. The reversal of 21244487 is 78444212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21244487 - 2⁸ = 21244231 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 (21244481) 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, 965648 + ... + 965669.

It is an arithmetic number, because the mean of its divisors is an integer number (5793954).

Almost surely, 2^21244487 is an apocalyptic number.

21244487 is a deficient number, since it is larger than the sum of its proper divisors (1931329).

21244487 is a wasteful number, since it uses less digits than its factorization.

21244487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1931328.

The product of its digits is 14336, while the sum is 32.

The square root of 21244487 is about 4609.1742210509. The cubic root of 21244487 is about 276.9589577182.

Adding to 21244487 its reverse (78444212), we get a palindrome (99688699).

The spelling of 21244487 in words is "twenty-one million, two hundred forty-four thousand, four hundred eighty-seven".