21440487 has 4 divisors (see below), whose sum is σ = 28587320. Its totient is φ = 14293656.

The previous prime is 21440473. The next prime is 21440491. The reversal of 21440487 is 78404412.

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

It is not a de Polignac number, because 21440487 - 2¹⁰ = 21439463 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 (21440087) 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, 3573412 + ... + 3573417.

It is an arithmetic number, because the mean of its divisors is an integer number (7146830).

Almost surely, 2^21440487 is an apocalyptic number.

21440487 is a deficient number, since it is larger than the sum of its proper divisors (7146833).

21440487 is an equidigital number, since it uses as much as digits as its factorization.

21440487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7146832.

The product of its (nonzero) digits is 7168, while the sum is 30.

The square root of 21440487 is about 4630.3873488079. The cubic root of 21440487 is about 277.8080857182.

Adding to 21440487 its reverse (78404412), we get a palindrome (99844899).

The spelling of 21440487 in words is "twenty-one million, four hundred forty thousand, four hundred eighty-seven".