20781997 has 8 divisors (see below), whose sum is σ = 21542400. Its totient is φ = 20027280.

The previous prime is 20781931. The next prime is 20782031. The reversal of 20781997 is 79918702.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20781997 - 2¹⁵ = 20749229 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20781697) 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, 6879 + ... + 9427.

It is an arithmetic number, because the mean of its divisors is an integer number (2692800).

Almost surely, 2^20781997 is an apocalyptic number.

It is an amenable number.

20781997 is a deficient number, since it is larger than the sum of its proper divisors (760403).

20781997 is a wasteful number, since it uses less digits than its factorization.

20781997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2843.

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

The square root of 20781997 is about 4558.7275636958. The cubic root of 20781997 is about 274.9344063943.

The spelling of 20781997 in words is "twenty million, seven hundred eighty-one thousand, nine hundred ninety-seven".