21004002 has 16 divisors (see below), whose sum is σ = 46675680. Its totient is φ = 7001316.

The previous prime is 21003937. The next prime is 21004043. The reversal of 21004002 is 20040012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 194428 + ... + 194535.

It is an arithmetic number, because the mean of its divisors is an integer number (2917230).

Almost surely, 2^21004002 is an apocalyptic number.

21004002 is an abundant number, since it is smaller than the sum of its proper divisors (25671678).

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

21004002 is a wasteful number, since it uses less digits than its factorization.

21004002 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388974 (or 388968 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 9.

The square root of 21004002 is about 4583.0123281527. The cubic root of 21004002 is about 275.9099422623.

Adding to 21004002 its reverse (20040012), we get a palindrome (41044014).

It can be divided in two parts, 2 and 1004002, that added together give a square (1004004 = 1002²).

The spelling of 21004002 in words is "twenty-one million, four thousand, two".