621891 has 16 divisors (see below), whose sum is σ = 952320. Its totient is φ = 400680.

The previous prime is 621883. The next prime is 621893. The reversal of 621891 is 198126.

It is not a de Polignac number, because 621891 - 2³ = 621883 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

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 (621893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 466 + ... + 1208.

It is an arithmetic number, because the mean of its divisors is an integer number (59520).

2⁶²¹⁸⁹¹ is an apocalyptic number.

621891 is a deficient number, since it is larger than the sum of its proper divisors (330429).

621891 is a wasteful number, since it uses less digits than its factorization.

621891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 783 (or 777 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 621891 is about 788.6006593961. The cubic root of 621891 is about 85.3567932053.

It can be divided in two parts, 62 and 1891, that added together give a triangular number (1953 = T₆₂).

The spelling of 621891 in words is "six hundred twenty-one thousand, eight hundred ninety-one".