21609460 has 72 divisors (see below), whose sum is σ = 49734216. Its totient is φ = 7879680.

The previous prime is 21609439. The next prime is 21609461. The reversal of 21609460 is 6490612.

It can be written as a sum of positive squares in 4 ways, for example, as 116964 + 21492496 = 342^2 + 4636^2 .

It is a super-2 number, since 2×21609460² = 933937522983200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21609461) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 295984 + ... + 296056.

It is an arithmetic number, because the mean of its divisors is an integer number (690753).

Almost surely, 2^21609460 is an apocalyptic number.

21609460 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21609460, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24867108).

21609460 is an abundant number, since it is smaller than the sum of its proper divisors (28124756).

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

21609460 is a wasteful number, since it uses less digits than its factorization.

21609460 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161 (or 140 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21609460 is about 4648.5976379979. The cubic root of 21609460 is about 278.5359809628.

The spelling of 21609460 in words is "twenty-one million, six hundred nine thousand, four hundred sixty".