21316487 has 4 divisors (see below), whose sum is σ = 22570416. Its totient is φ = 20062560.

The previous prime is 21316483. The next prime is 21316501. The reversal of 21316487 is 78461312.

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 21316487 - 2² = 21316483 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 (21316481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 626939 + ... + 626972.

It is an arithmetic number, because the mean of its divisors is an integer number (5642604).

Almost surely, 2^21316487 is an apocalyptic number.

21316487 is a deficient number, since it is larger than the sum of its proper divisors (1253929).

21316487 is a wasteful number, since it uses less digits than its factorization.

21316487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1253928.

The product of its digits is 8064, while the sum is 32.

The square root of 21316487 is about 4616.9781242713. The cubic root of 21316487 is about 277.2714867958.

Adding to 21316487 its reverse (78461312), we get a palindrome (99777799).

The spelling of 21316487 in words is "twenty-one million, three hundred sixteen thousand, four hundred eighty-seven".