621981 has 6 divisors (see below), whose sum is σ = 898430. Its totient is φ = 414648.

The previous prime is 621941. The next prime is 621983. The reversal of 621981 is 189126.

It can be written as a sum of positive squares in only one way, i.e., 549081 + 72900 = 741^2 + 270^2 .

It is not a de Polignac number, because 621981 - 2¹⁰ = 620957 is a prime.

It is a super-2 number, since 2×621981² = 773720728722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (621983) 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 5 ways as a sum of consecutive naturals, for example, 34546 + ... + 34563.

2⁶²¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

621981 is a deficient number, since it is larger than the sum of its proper divisors (276449).

621981 is a wasteful number, since it uses less digits than its factorization.

621981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69115 (or 69112 counting only the distinct ones).

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

The square root of 621981 is about 788.6577204339. The cubic root of 621981 is about 85.3609106154.

The spelling of 621981 in words is "six hundred twenty-one thousand, nine hundred eighty-one".