8219781 has 6 divisors (see below), whose sum is σ = 11873030. Its totient is φ = 5479848.

The previous prime is 8219779. The next prime is 8219791. The reversal of 8219781 is 1879128.

It can be written as a sum of positive squares in only one way, i.e., 5447556 + 2772225 = 2334^2 + 1665^2 .

It is not a de Polignac number, because 8219781 - 2¹ = 8219779 is a prime.

It is a super-2 number, since 2×8219781² = 135129599375922, 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 (8219711) 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, 456646 + ... + 456663.

Almost surely, 2^8219781 is an apocalyptic number.

It is an amenable number.

8219781 is a deficient number, since it is larger than the sum of its proper divisors (3653249).

8219781 is a wasteful number, since it uses less digits than its factorization.

8219781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913315 (or 913312 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 8219781 is about 2867.0160446011. The cubic root of 8219781 is about 201.8149876091.

The spelling of 8219781 in words is "eight million, two hundred nineteen thousand, seven hundred eighty-one".