20799781 has 4 divisors (see below), whose sum is σ = 20880972. Its totient is φ = 20718592.

The previous prime is 20799769. The next prime is 20799799. The reversal of 20799781 is 18799702.

It is a happy number.

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 15920100 + 4879681 = 3990^2 + 2209^2 .

It is a cyclic number.

It is not a de Polignac number, because 20799781 - 2⁹ = 20799269 is a prime.

It is a super-2 number, since 2×20799781² = 865261779295922, 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 (20799731) 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, 40210 + ... + 40723.

It is an arithmetic number, because the mean of its divisors is an integer number (5220243).

Almost surely, 2^20799781 is an apocalyptic number.

It is an amenable number.

20799781 is a deficient number, since it is larger than the sum of its proper divisors (81191).

20799781 is an equidigital number, since it uses as much as digits as its factorization.

20799781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81190.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 20799781 is about 4560.6776908701. The cubic root of 20799781 is about 275.0128082189.

The spelling of 20799781 in words is "twenty million, seven hundred ninety-nine thousand, seven hundred eighty-one".