21512106 has 144 divisors (see below), whose sum is σ = 62741952. Its totient is φ = 5195520.

The previous prime is 21512093. The next prime is 21512129. The reversal of 21512106 is 60121512.

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

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 259141 + ... + 259223.

It is an arithmetic number, because the mean of its divisors is an integer number (435708).

Almost surely, 2^21512106 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21512106, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31370976).

21512106 is an abundant number, since it is smaller than the sum of its proper divisors (41229846).

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

21512106 is a wasteful number, since it uses less digits than its factorization.

21512106 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137 (or 123 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21512106 is about 4638.1144875908. The cubic root of 21512106 is about 278.1170685109.

Adding to 21512106 its reverse (60121512), we get a palindrome (81633618).

It can be divided in two parts, 215 and 12106, that added together give a palindrome (12321).

The spelling of 21512106 in words is "twenty-one million, five hundred twelve thousand, one hundred six".