21251632 has 80 divisors (see below), whose sum is σ = 47139840. Its totient is φ = 9225216.

The previous prime is 21251617. The next prime is 21251669. The reversal of 21251632 is 23615212.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 268969 + ... + 269047.

It is an arithmetic number, because the mean of its divisors is an integer number (589248).

Almost surely, 2^21251632 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21251632, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23569920).

21251632 is an abundant number, since it is smaller than the sum of its proper divisors (25888208).

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

21251632 is a wasteful number, since it uses less digits than its factorization.

21251632 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170 (or 164 counting only the distinct ones).

The product of its digits is 720, while the sum is 22.

The square root of 21251632 is about 4609.9492405015. The cubic root of 21251632 is about 276.9900034188.

Adding to 21251632 its reverse (23615212), we get a palindrome (44866844).

The spelling of 21251632 in words is "twenty-one million, two hundred fifty-one thousand, six hundred thirty-two".