205721020 has 48 divisors (see below), whose sum is σ = 438848928. Its totient is φ = 80998400.

The previous prime is 205720979. The next prime is 205721069. The reversal of 205721020 is 20127502.

It is a super-2 number, since 2×205721020² = 84642276139680800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 512820 + ... + 513220.

It is an arithmetic number, because the mean of its divisors is an integer number (9142686).

Almost surely, 2^205721020 is an apocalyptic number.

205721020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

205721020 is an abundant number, since it is smaller than the sum of its proper divisors (233127908).

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

205721020 is a wasteful number, since it uses less digits than its factorization.

205721020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750 (or 748 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 205721020 is about 14342.9780729108. The cubic root of 205721020 is about 590.3273296168.

Adding to 205721020 its reverse (20127502), we get a palindrome (225848522).

The spelling of 205721020 in words is "two hundred five million, seven hundred twenty-one thousand, twenty".