21775819 has 12 divisors (see below), whose sum is σ = 23716800. Its totient is φ = 19984224.

The previous prime is 21775811. The next prime is 21775823. The reversal of 21775819 is 91857712.

It is not a de Polignac number, because 21775819 - 2³ = 21775811 is a prime.

It is a super-2 number, since 2×21775819² = 948372586241522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21775811) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 45222 + ... + 45700.

It is an arithmetic number, because the mean of its divisors is an integer number (1976400).

Almost surely, 2^21775819 is an apocalyptic number.

21775819 is a deficient number, since it is larger than the sum of its proper divisors (1940981).

21775819 is a wasteful number, since it uses less digits than its factorization.

21775819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 774 (or 761 counting only the distinct ones).

The product of its digits is 35280, while the sum is 40.

The square root of 21775819 is about 4666.4567928997. The cubic root of 21775819 is about 279.2489181958.

The spelling of 21775819 in words is "twenty-one million, seven hundred seventy-five thousand, eight hundred nineteen".