21521130 has 64 divisors (see below), whose sum is σ = 54217728. Its totient is φ = 5460480.

The previous prime is 21521117. The next prime is 21521141. The reversal of 21521130 is 3112512.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 67732 + ... + 68048.

It is an arithmetic number, because the mean of its divisors is an integer number (847152).

Almost surely, 2^21521130 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21521130, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27108864).

21521130 is an abundant number, since it is smaller than the sum of its proper divisors (32696598).

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

21521130 is a wasteful number, since it uses less digits than its factorization.

21521130 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 431.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21521130 is about 4639.0871946968. The cubic root of 21521130 is about 278.1559516957.

Adding to 21521130 its reverse (3112512), we get a palindrome (24633642).

The spelling of 21521130 in words is "twenty-one million, five hundred twenty-one thousand, one hundred thirty".