819977661 has 40 divisors (see below), whose sum is σ = 1292918880. Its totient is φ = 516458592.

The previous prime is 819977633. The next prime is 819977663. The reversal of 819977661 is 166779918.

It is not a de Polignac number, because 819977661 - 2⁵ = 819977629 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 819977598 and 819977607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (819977663) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1041510 + ... + 1042296.

It is an arithmetic number, because the mean of its divisors is an integer number (32322972).

Almost surely, 2^819977661 is an apocalyptic number.

819977661 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

819977661 is a deficient number, since it is larger than the sum of its proper divisors (472941219).

819977661 is a wasteful number, since it uses less digits than its factorization.

819977661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1495 (or 1486 counting only the distinct ones).

The product of its digits is 1143072, while the sum is 54.

The square root of 819977661 is about 28635.2520680367. The cubic root of 819977661 is about 935.9816626092.

The spelling of 819977661 in words is "eight hundred nineteen million, nine hundred seventy-seven thousand, six hundred sixty-one".