21131008 has 36 divisors (see below), whose sum is σ = 42494760. Its totient is φ = 10486784.

The previous prime is 21130987. The next prime is 21131009. The reversal of 21131008 is 80013112.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 21130982 and 21131000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131009) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50223 + ... + 50641.

It is an arithmetic number, because the mean of its divisors is an integer number (1180410).

Almost surely, 2^21131008 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21131008, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21247380).

21131008 is an abundant number, since it is smaller than the sum of its proper divisors (21363752).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21131008 is an equidigital number, since it uses as much as digits as its factorization.

21131008 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 632 (or 618 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 16.

The square root of 21131008 is about 4596.8476154861. The cubic root of 21131008 is about 276.4649448106.

It can be divided in two parts, 2 and 1131008, that multiplied together give a square (2262016 = 1504²).

The spelling of 21131008 in words is "twenty-one million, one hundred thirty-one thousand, eight".