21813797 has 4 divisors (see below), whose sum is σ = 21828876. Its totient is φ = 21798720.

The previous prime is 21813761. The next prime is 21813809. The reversal of 21813797 is 79731812.

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

It can be written as a sum of positive squares in 2 ways, for example, as 20376196 + 1437601 = 4514^2 + 1199^2 .

It is a cyclic number.

It is not a de Polignac number, because 21813797 - 2¹⁶ = 21748261 is a prime.

It is a super-4 number, since 4×21813797⁴ (a number of 30 digits) contains 4444 as substring.

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 21813797.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21813097) 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, 5108 + ... + 8349.

It is an arithmetic number, because the mean of its divisors is an integer number (5457219).

Almost surely, 2^21813797 is an apocalyptic number.

It is an amenable number.

21813797 is a deficient number, since it is larger than the sum of its proper divisors (15079).

21813797 is a wasteful number, since it uses less digits than its factorization.

21813797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15078.

The product of its digits is 21168, while the sum is 38.

The square root of 21813797 is about 4670.5242746398. The cubic root of 21813797 is about 279.4111647685.

The spelling of 21813797 in words is "twenty-one million, eight hundred thirteen thousand, seven hundred ninety-seven".