21453531 has 8 divisors (see below), whose sum is σ = 31205184. Its totient is φ = 13002120.

The previous prime is 21453529. The next prime is 21453559. The reversal of 21453531 is 13535412.

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

It is not a de Polignac number, because 21453531 - 2¹ = 21453529 is a prime.

It is a super-2 number, since 2×21453531² = 920507984735922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21453331) 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, 325021 + ... + 325086.

It is an arithmetic number, because the mean of its divisors is an integer number (3900648).

Almost surely, 2^21453531 is an apocalyptic number.

21453531 is a deficient number, since it is larger than the sum of its proper divisors (9751653).

21453531 is a wasteful number, since it uses less digits than its factorization.

21453531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 650121.

The product of its digits is 1800, while the sum is 24.

The square root of 21453531 is about 4631.7956561144. The cubic root of 21453531 is about 277.8644120826.

Adding to 21453531 its reverse (13535412), we get a palindrome (34988943).

The spelling of 21453531 in words is "twenty-one million, four hundred fifty-three thousand, five hundred thirty-one".