21531008 has 16 divisors (see below), whose sum is σ = 42894060. Its totient is φ = 10765440.

The previous prime is 21531001. The next prime is 21531011. The reversal of 21531008 is 80013512.

It is a tau number, because it is divible by the number of its divisors (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83978 + ... + 84233.

Almost surely, 2^21531008 is an apocalyptic number.

It is an amenable number.

21531008 is a deficient number, since it is larger than the sum of its proper divisors (21363052).

21531008 is an equidigital number, since it uses as much as digits as its factorization.

21531008 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168225 (or 168213 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21531008 is about 4640.1517216574. The cubic root of 21531008 is about 278.1985021910.

The spelling of 21531008 in words is "twenty-one million, five hundred thirty-one thousand, eight".