21531006 has 24 divisors (see below), whose sum is σ = 53315184. Its totient is φ = 6151680.

The previous prime is 21531001. The next prime is 21531011. The reversal of 21531006 is 60013512.

It is an interprime number because it is at equal distance from previous prime (21531001) and next prime (21531011).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a self number, because there is not a number n which added to its sum of digits gives 21531006.

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 polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 85315 + ... + 85566.

It is an arithmetic number, because the mean of its divisors is an integer number (2221466).

Almost surely, 2^21531006 is an apocalyptic number.

21531006 is an abundant number, since it is smaller than the sum of its proper divisors (31784178).

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

21531006 is a wasteful number, since it uses less digits than its factorization.

21531006 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170896 (or 170893 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21531006 is about 4640.1515061472. The cubic root of 21531006 is about 278.1984935771.

Adding to 21531006 its reverse (60013512), we get a palindrome (81544518).

The spelling of 21531006 in words is "twenty-one million, five hundred thirty-one thousand, six".