21002504 has 8 divisors (see below), whose sum is σ = 39379710. Its totient is φ = 10501248.

The previous prime is 21002503. The next prime is 21002507. The reversal of 21002504 is 40520012.

It can be written as a sum of positive squares in only one way, i.e., 15194404 + 5808100 = 3898^2 + 2410^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×21002504² = 882210348540032, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21002503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1312649 + ... + 1312664.

Almost surely, 2^21002504 is an apocalyptic number.

It is an amenable number.

21002504 is a deficient number, since it is larger than the sum of its proper divisors (18377206).

21002504 is a wasteful number, since it uses less digits than its factorization.

21002504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2625319 (or 2625315 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 21002504 is about 4582.8488956107. The cubic root of 21002504 is about 275.9033828311.

Adding to 21002504 its reverse (40520012), we get a palindrome (61522516).

The spelling of 21002504 in words is "twenty-one million, two thousand, five hundred four".