621691 has 4 divisors (see below), whose sum is σ = 710512. Its totient is φ = 532872.

The previous prime is 621679. The next prime is 621697. The reversal of 621691 is 196126.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 621691 - 2¹³ = 613499 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (621697) 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 3 ways as a sum of consecutive naturals, for example, 44400 + ... + 44413.

It is an arithmetic number, because the mean of its divisors is an integer number (177628).

2⁶²¹⁶⁹¹ is an apocalyptic number.

621691 is a deficient number, since it is larger than the sum of its proper divisors (88821).

621691 is an equidigital number, since it uses as much as digits as its factorization.

621691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 88820.

The product of its digits is 648, while the sum is 25.

The square root of 621691 is about 788.4738423055. The cubic root of 621691 is about 85.3476419827.

The spelling of 621691 in words is "six hundred twenty-one thousand, six hundred ninety-one".