21820779 has 8 divisors (see below), whose sum is σ = 32327120. Its totient is φ = 14547168.

The previous prime is 21820769. The next prime is 21820781. The reversal of 21820779 is 97702812.

It is not a de Polignac number, because 21820779 - 2⁸ = 21820523 is a prime.

It is a super-2 number, since 2×21820779² = 952292792333682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820709) 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, 404062 + ... + 404115.

It is an arithmetic number, because the mean of its divisors is an integer number (4040890).

Almost surely, 2^21820779 is an apocalyptic number.

21820779 is a deficient number, since it is larger than the sum of its proper divisors (10506341).

21820779 is an equidigital number, since it uses as much as digits as its factorization.

21820779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 808186 (or 808180 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 21820779 is about 4671.2716684004. The cubic root of 21820779 is about 279.4409722133.

The spelling of 21820779 in words is "twenty-one million, eight hundred twenty thousand, seven hundred seventy-nine".