621778 has 4 divisors (see below), whose sum is σ = 932670. Its totient is φ = 310888.

The previous prime is 621769. The next prime is 621779. The reversal of 621778 is 877126.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 588289 + 33489 = 767^2 + 183^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (621779) 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 as a sum of consecutive naturals, namely, 155443 + ... + 155446.

2⁶²¹⁷⁷⁸ is an apocalyptic number.

621778 is a deficient number, since it is larger than the sum of its proper divisors (310892).

621778 is a wasteful number, since it uses less digits than its factorization.

621778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310891.

The product of its digits is 4704, while the sum is 31.

The square root of 621778 is about 788.5290102463. The cubic root of 621778 is about 85.3516230057.

The spelling of 621778 in words is "six hundred twenty-one thousand, seven hundred seventy-eight".