21147987 has 8 divisors (see below), whose sum is σ = 32225536. Its totient is φ = 12084552.

The previous prime is 21147967. The next prime is 21148013. The reversal of 21147987 is 78974112.

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

It is a de Polignac number, because none of the positive numbers 2^k-21147987 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21147937) 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 7 ways as a sum of consecutive naturals, for example, 503503 + ... + 503544.

It is an arithmetic number, because the mean of its divisors is an integer number (4028192).

Almost surely, 2^21147987 is an apocalyptic number.

21147987 is a deficient number, since it is larger than the sum of its proper divisors (11077549).

21147987 is a wasteful number, since it uses less digits than its factorization.

21147987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1007057.

The product of its digits is 28224, while the sum is 39.

The square root of 21147987 is about 4598.6940537505. The cubic root of 21147987 is about 276.5389725397.

It can be divided in two parts, 2114 and 7987, that added together give a palindrome (10101).

The spelling of 21147987 in words is "twenty-one million, one hundred forty-seven thousand, nine hundred eighty-seven".