21005004 has 24 divisors (see below), whose sum is σ = 49130928. Its totient is φ = 6984640.

The previous prime is 21004999. The next prime is 21005009. The reversal of 21005004 is 40050012.

It is an interprime number because it is at equal distance from previous prime (21004999) and next prime (21005009).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is not an unprimeable number, because it can be changed into a prime (21005009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3634 + ... + 7430.

It is an arithmetic number, because the mean of its divisors is an integer number (2047122).

Almost surely, 2^21005004 is an apocalyptic number.

It is an amenable number.

21005004 is an abundant number, since it is smaller than the sum of its proper divisors (28125924).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21005004 is a wasteful number, since it uses less digits than its factorization.

21005004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4265 (or 4263 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 21005004 is about 4583.1216435962. The cubic root of 21005004 is about 275.9143296384.

Adding to 21005004 its reverse (40050012), we get a palindrome (61055016).

The spelling of 21005004 in words is "twenty-one million, five thousand, four".