21581936 has 10 divisors (see below), whose sum is σ = 41815032. Its totient is φ = 10790960.

The previous prime is 21581927. The next prime is 21581947. The reversal of 21581936 is 63918512.

It is a junction number, because it is equal to n+sod(n) for n = 21581896 and 21581905.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 674420 + ... + 674451.

Almost surely, 2^21581936 is an apocalyptic number.

It is an amenable number.

21581936 is a deficient number, since it is larger than the sum of its proper divisors (20233096).

21581936 is a wasteful number, since it uses less digits than its factorization.

21581936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1348879 (or 1348873 counting only the distinct ones).

The product of its digits is 12960, while the sum is 35.

The square root of 21581936 is about 4645.6362319923. The cubic root of 21581936 is about 278.4176734938.

The spelling of 21581936 in words is "twenty-one million, five hundred eighty-one thousand, nine hundred thirty-six".