21004587 has 12 divisors (see below), whose sum is σ = 31080504. Its totient is φ = 13661280.

The previous prime is 21004583. The next prime is 21004591. The reversal of 21004587 is 78540012.

It is an interprime number because it is at equal distance from previous prime (21004583) and next prime (21004591).

It is not a de Polignac number, because 21004587 - 2² = 21004583 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21004587.

It is not an unprimeable number, because it can be changed into a prime (21004583) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28093 + ... + 28830.

It is an arithmetic number, because the mean of its divisors is an integer number (2590042).

Almost surely, 2^21004587 is an apocalyptic number.

21004587 is a deficient number, since it is larger than the sum of its proper divisors (10075917).

21004587 is a wasteful number, since it uses less digits than its factorization.

21004587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56970 (or 56967 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21004587 is about 4583.0761503601. The cubic root of 21004587 is about 275.9125037713.

Adding to 21004587 its reverse (78540012), we get a palindrome (99544599).

The spelling of 21004587 in words is "twenty-one million, four thousand, five hundred eighty-seven".