21004531 has 8 divisors (see below), whose sum is σ = 21432240. Its totient is φ = 20579328.

The previous prime is 21004517. The next prime is 21004541. The reversal of 21004531 is 13540012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21004531 - 2⁵ = 21004499 is a prime.

It is a super-2 number, since 2×21004531² = 882380645059922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21004541) 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, 33735 + ... + 34351.

It is an arithmetic number, because the mean of its divisors is an integer number (2679030).

Almost surely, 2^21004531 is an apocalyptic number.

21004531 is a deficient number, since it is larger than the sum of its proper divisors (427709).

21004531 is an equidigital number, since it uses as much as digits as its factorization.

21004531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1253.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21004531 is about 4583.0700409224. The cubic root of 21004531 is about 275.9122585691.

Adding to 21004531 its reverse (13540012), we get a palindrome (34544543).

The spelling of 21004531 in words is "twenty-one million, four thousand, five hundred thirty-one".