820621663 has 4 divisors (see below), whose sum is σ = 822394528. Its totient is φ = 818848800.

The previous prime is 820621639. The next prime is 820621679. The reversal of 820621663 is 366126028.

It is a happy number.

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 820621663 - 2¹³ = 820613471 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 (820621693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 885738 + ... + 886663.

It is an arithmetic number, because the mean of its divisors is an integer number (205598632).

Almost surely, 2^820621663 is an apocalyptic number.

820621663 is a deficient number, since it is larger than the sum of its proper divisors (1772865).

820621663 is a wasteful number, since it uses less digits than its factorization.

820621663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1772864.

The product of its (nonzero) digits is 20736, while the sum is 34.

The square root of 820621663 is about 28646.4947768484. The cubic root of 820621663 is about 936.2266352696.

The spelling of 820621663 in words is "eight hundred twenty million, six hundred twenty-one thousand, six hundred sixty-three".