21787768 has 16 divisors (see below), whose sum is σ = 41235480. Its totient is φ = 10791648.

The previous prime is 21787763. The next prime is 21787771. The reversal of 21787768 is 86778712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21787763) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11871 + ... + 13582.

Almost surely, 2^21787768 is an apocalyptic number.

It is an amenable number.

21787768 is a deficient number, since it is larger than the sum of its proper divisors (19447712).

21787768 is a wasteful number, since it uses less digits than its factorization.

21787768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25566 (or 25562 counting only the distinct ones).

The product of its digits is 263424, while the sum is 46.

The square root of 21787768 is about 4667.7369248920. The cubic root of 21787768 is about 279.2999860827.

The spelling of 21787768 in words is "twenty-one million, seven hundred eighty-seven thousand, seven hundred sixty-eight".