21251630 has 8 divisors (see below), whose sum is σ = 38252952. Its totient is φ = 8500648.

The previous prime is 21251617. The next prime is 21251669. The reversal of 21251630 is 3615212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1062572 + ... + 1062591.

It is an arithmetic number, because the mean of its divisors is an integer number (4781619).

Almost surely, 2^21251630 is an apocalyptic number.

21251630 is a deficient number, since it is larger than the sum of its proper divisors (17001322).

21251630 is a wasteful number, since it uses less digits than its factorization.

21251630 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2125170.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21251630 is about 4609.9490235793. The cubic root of 21251630 is about 276.9899947296.

Adding to 21251630 its reverse (3615212), we get a palindrome (24866842).

The spelling of 21251630 in words is "twenty-one million, two hundred fifty-one thousand, six hundred thirty".