205421643 has 32 divisors (see below), whose sum is σ = 348902400. Its totient is φ = 117013248.

The previous prime is 205421641. The next prime is 205421647. The reversal of 205421643 is 346124502.

It is not a de Polignac number, because 205421643 - 2¹ = 205421641 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (205421641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 65178 + ... + 68256.

It is an arithmetic number, because the mean of its divisors is an integer number (10903200).

Almost surely, 2^205421643 is an apocalyptic number.

205421643 is a deficient number, since it is larger than the sum of its proper divisors (143480757).

205421643 is a wasteful number, since it uses less digits than its factorization.

205421643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3448 (or 3442 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 205421643 is about 14332.5379120378. The cubic root of 205421643 is about 590.0408312257.

The spelling of 205421643 in words is "two hundred five million, four hundred twenty-one thousand, six hundred forty-three".