21768819 has 8 divisors (see below), whose sum is σ = 29422992. Its totient is φ = 14313600.

The previous prime is 21768811. The next prime is 21768847. The reversal of 21768819 is 91886712.

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

It is not a de Polignac number, because 21768819 - 2³ = 21768811 is a prime.

It is a super-2 number, since 2×21768819² = 947762961309522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21768811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49482 + ... + 49919.

It is an arithmetic number, because the mean of its divisors is an integer number (3677874).

Almost surely, 2^21768819 is an apocalyptic number.

21768819 is a deficient number, since it is larger than the sum of its proper divisors (7654173).

21768819 is an equidigital number, since it uses as much as digits as its factorization.

21768819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99477.

The product of its digits is 48384, while the sum is 42.

The square root of 21768819 is about 4665.7066988828. The cubic root of 21768819 is about 279.2189927707.

The spelling of 21768819 in words is "twenty-one million, seven hundred sixty-eight thousand, eight hundred nineteen".