677821 has 4 divisors (see below), whose sum is σ = 679644. Its totient is φ = 676000.

The previous prime is 677813. The next prime is 677827. The reversal of 677821 is 128776.

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 2 ways, for example, as 60025 + 617796 = 245^2 + 786^2 .

It is a 3-Lehmer number, since φ(677821) divides (677821-1)³.

It is a cyclic number.

It is not a de Polignac number, because 677821 - 2³ = 677813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (677827) 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, 130 + ... + 1171.

It is an arithmetic number, because the mean of its divisors is an integer number (169911).

2⁶⁷⁷⁸²¹ is an apocalyptic number.

677821 is the 521-st heptagonal number.

It is an amenable number.

677821 is a deficient number, since it is larger than the sum of its proper divisors (1823).

677821 is a wasteful number, since it uses less digits than its factorization.

677821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1822.

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

The square root of 677821 is about 823.2988521795. The cubic root of 677821 is about 87.8425645843.

The spelling of 677821 in words is "six hundred seventy-seven thousand, eight hundred twenty-one".