654991 has 2 divisors, whose sum is σ = 654992. Its totient is φ = 654990.

The previous prime is 654967. The next prime is 655001. The reversal of 654991 is 199456.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 654991 - 2¹¹ = 652943 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (654931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 327495 + 327496.

It is an arithmetic number, because the mean of its divisors is an integer number (327496).

2⁶⁵⁴⁹⁹¹ is an apocalyptic number.

654991 is a deficient number, since it is larger than the sum of its proper divisors (1).

654991 is an equidigital number, since it uses as much as digits as its factorization.

654991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9720, while the sum is 34.

The square root of 654991 is about 809.3151425743. The cubic root of 654991 is about 86.8450582599.

Subtracting from 654991 its reverse (199456), we obtain a triangular number (455535 = T₉₅₄).

It can be divided in two parts, 65 and 4991, that multiplied together give a triangular number (324415 = T₈₀₅).

The spelling of 654991 in words is "six hundred fifty-four thousand, nine hundred ninety-one".