21001231 has 8 divisors (see below), whose sum is σ = 22063104. Its totient is φ = 19951800.

The previous prime is 21001187. The next prime is 21001247. The reversal of 21001231 is 13210012.

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 21001231 - 2¹³ = 20993039 is a prime.

It is a super-2 number, since 2×21001231² = 882103407030722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001531) 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, 450 + ... + 6496.

It is an arithmetic number, because the mean of its divisors is an integer number (2757888).

Almost surely, 2^21001231 is an apocalyptic number.

21001231 is a deficient number, since it is larger than the sum of its proper divisors (1061873).

21001231 is a wasteful number, since it uses less digits than its factorization.

21001231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6221.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21001231 is about 4582.7100060990. The cubic root of 21001231 is about 275.8978083830.

Adding to 21001231 its reverse (13210012), we get a palindrome (34211243).

The spelling of 21001231 in words is "twenty-one million, one thousand, two hundred thirty-one".