206721004997 has 20 divisors (see below), whose sum is σ = 227017211100. Its totient is φ = 188203526784.

The previous prime is 206721004981. The next prime is 206721005017. The reversal of 206721004997 is 799400127602.

It can be written as a sum of positive squares in 10 ways, for example, as 198019660036 + 8701344961 = 444994^2 + 93281^2 .

It is not a de Polignac number, because 206721004997 - 2⁴ = 206721004981 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 (206721054997) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 2035379 + ... + 2134527.

It is an arithmetic number, because the mean of its divisors is an integer number (11350860555).

Almost surely, 2^206721004997 is an apocalyptic number.

It is an amenable number.

206721004997 is a deficient number, since it is larger than the sum of its proper divisors (20296206103).

206721004997 is an frugal number, since it uses more digits than its factorization.

206721004997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99274 (or 99235 counting only the distinct ones).

The product of its (nonzero) digits is 381024, while the sum is 47.

The spelling of 206721004997 in words is "two hundred six billion, seven hundred twenty-one million, four thousand, nine hundred ninety-seven".