21768907 has 4 divisors (see below), whose sum is σ = 21793816. Its totient is φ = 21744000.

The previous prime is 21768893. The next prime is 21768911. The reversal of 21768907 is 70986712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21768907 - 2⁷ = 21768779 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21768907.

It is not an unprimeable number, because it can be changed into a prime (21768917) 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, 11094 + ... + 12907.

It is an arithmetic number, because the mean of its divisors is an integer number (5448454).

Almost surely, 2^21768907 is an apocalyptic number.

21768907 is a deficient number, since it is larger than the sum of its proper divisors (24909).

21768907 is an equidigital number, since it uses as much as digits as its factorization.

21768907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24908.

The product of its (nonzero) digits is 42336, while the sum is 40.

The square root of 21768907 is about 4665.7161293846. The cubic root of 21768907 is about 279.2193690159.

The spelling of 21768907 in words is "twenty-one million, seven hundred sixty-eight thousand, nine hundred seven".