21031008 has 48 divisors (see below), whose sum is σ = 55981296. Its totient is φ = 6912000.

The previous prime is 21030979. The next prime is 21031009. The reversal of 21031008 is 80013012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031009) 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, 5508 + ... + 8508.

It is an arithmetic number, because the mean of its divisors is an integer number (1166277).

Almost surely, 2^21031008 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 21031008, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27990648).

21031008 is an abundant number, since it is smaller than the sum of its proper divisors (34950288).

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

21031008 is a wasteful number, since it uses less digits than its factorization.

21031008 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3087 (or 3079 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21031008 is about 4585.9576971446. The cubic root of 21031008 is about 276.0281424780.

The spelling of 21031008 in words is "twenty-one million, thirty-one thousand, eight".