21787936 has 12 divisors (see below), whose sum is σ = 42895062. Its totient is φ = 10893952.

The previous prime is 21787907. The next prime is 21787939. The reversal of 21787936 is 63978712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 17139600 + 4648336 = 4140^2 + 2156^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21787892 and 21787901.

It is not an unprimeable number, because it can be changed into a prime (21787939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340405 + ... + 340468.

Almost surely, 2^21787936 is an apocalyptic number.

It is an amenable number.

21787936 is a deficient number, since it is larger than the sum of its proper divisors (21107126).

21787936 is an equidigital number, since it uses as much as digits as its factorization.

21787936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 680883 (or 680875 counting only the distinct ones).

The product of its digits is 127008, while the sum is 43.

The square root of 21787936 is about 4667.7549207301. The cubic root of 21787936 is about 279.3007039515.

The spelling of 21787936 in words is "twenty-one million, seven hundred eighty-seven thousand, nine hundred thirty-six".