21819797 has 4 divisors (see below), whose sum is σ = 22284096. Its totient is φ = 21355500.

The previous prime is 21819781. The next prime is 21819799. The reversal of 21819797 is 79791812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21819797 - 2⁴ = 21819781 is a prime.

It is a super-2 number, since 2×21819797² = 952207082242418, 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 (21819799) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 232079 + ... + 232172.

It is an arithmetic number, because the mean of its divisors is an integer number (5571024).

Almost surely, 2^21819797 is an apocalyptic number.

It is an amenable number.

21819797 is a deficient number, since it is larger than the sum of its proper divisors (464299).

21819797 is an equidigital number, since it uses as much as digits as its factorization.

21819797 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 464298.

The product of its digits is 63504, while the sum is 44.

The square root of 21819797 is about 4671.1665566537. The cubic root of 21819797 is about 279.4367802586.

The spelling of 21819797 in words is "twenty-one million, eight hundred nineteen thousand, seven hundred ninety-seven".