653991 has 16 divisors (see below), whose sum is σ = 964320. Its totient is φ = 391680.

The previous prime is 653977. The next prime is 653993. The reversal of 653991 is 199356.

It is not a de Polignac number, because 653991 - 2⁶ = 653927 is a prime.

653991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (653993) by changing a digit.

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, 1395 + ... + 1803.

It is an arithmetic number, because the mean of its divisors is an integer number (60270).

2⁶⁵³⁹⁹¹ is an apocalyptic number.

653991 is a deficient number, since it is larger than the sum of its proper divisors (310329).

653991 is a wasteful number, since it uses less digits than its factorization.

653991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 466.

The product of its digits is 7290, while the sum is 33.

The square root of 653991 is about 808.6971002792. The cubic root of 653991 is about 86.8008391829.

The spelling of 653991 in words is "six hundred fifty-three thousand, nine hundred ninety-one".