206561640 has 32 divisors (see below), whose sum is σ = 619685280. Its totient is φ = 55083072.

The previous prime is 206561633. The next prime is 206561647. The reversal of 206561640 is 46165602.

206561640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (206561633) and next prime (206561647).

It is a super-2 number, since 2×206561640² = 85335422238979200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 206561598 and 206561607.

It is not an unprimeable number, because it can be changed into a prime (206561647) 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, 860554 + ... + 860793.

It is an arithmetic number, because the mean of its divisors is an integer number (19365165).

Almost surely, 2^206561640 is an apocalyptic number.

206561640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

206561640 is an abundant number, since it is smaller than the sum of its proper divisors (413123640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

206561640 is a wasteful number, since it uses less digits than its factorization.

206561640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1721361 (or 1721357 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 206561640 is about 14372.2524330739. The cubic root of 206561640 is about 591.1303047245.

The spelling of 206561640 in words is "two hundred six million, five hundred sixty-one thousand, six hundred forty".