205721000 has 32 divisors (see below), whose sum is σ = 481389480. Its totient is φ = 82288000.

The previous prime is 205720979. The next prime is 205721069. The reversal of 205721000 is 127502.

It can be written as a sum of positive squares in 4 ways, for example, as 82555396 + 123165604 = 9086^2 + 11098^2 .

It is a super-2 number, since 2×205721000² = 84642259682000000, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 205721000.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 101861 + ... + 103860.

Almost surely, 2^205721000 is an apocalyptic number.

205721000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

205721000 is an abundant number, since it is smaller than the sum of its proper divisors (275668480).

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

205721000 is a wasteful number, since it uses less digits than its factorization.

205721000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205742 (or 205728 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 205721000 is about 14342.9773757055. The cubic root of 205721000 is about 590.3273104865.

Adding to 205721000 its reverse (127502), we get a palindrome (205848502).

The spelling of 205721000 in words is "two hundred five million, seven hundred twenty-one thousand".