21508470 has 64 divisors (see below), whose sum is σ = 58933440. Its totient is φ = 5577984.

The previous prime is 21508439. The next prime is 21508481. The reversal of 21508470 is 7480512.

It is a super-2 number, since 2×21508470² = 925228563481800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

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, 8914 + ... + 11066.

It is an arithmetic number, because the mean of its divisors is an integer number (920835).

Almost surely, 2^21508470 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21508470, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29466720).

21508470 is an abundant number, since it is smaller than the sum of its proper divisors (37424970).

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

21508470 is a wasteful number, since it uses less digits than its factorization.

21508470 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2206 (or 2200 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21508470 is about 4637.7225014009. The cubic root of 21508470 is about 278.1013984096.

Adding to 21508470 its reverse (7480512), we get a palindrome (28988982).

The spelling of 21508470 in words is "twenty-one million, five hundred eight thousand, four hundred seventy".