21021004 has 6 divisors (see below), whose sum is σ = 36786764. Its totient is φ = 10510500.

The previous prime is 21021001. The next prime is 21021043. The reversal of 21021004 is 40012012.

It is not an unprimeable number, because it can be changed into a prime (21021001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2627622 + ... + 2627629.

Almost surely, 2^21021004 is an apocalyptic number.

It is an amenable number.

21021004 is a deficient number, since it is larger than the sum of its proper divisors (15765760).

21021004 is a wasteful number, since it uses less digits than its factorization.

21021004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5255255 (or 5255253 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21021004 is about 4584.8668464853. The cubic root of 21021004 is about 275.9843686449.

Adding to 21021004 its reverse (40012012), we get a palindrome (61033016).

The spelling of 21021004 in words is "twenty-one million, twenty-one thousand, four".