6688131961 has 15 divisors (see below), whose sum is σ = 7807034031. Its totient is φ = 5729249736.

The previous prime is 6688131953. The next prime is 6688131973. The reversal of 6688131961 is 1691318866.

It is a happy number.

The square root of 6688131961 is 81781.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 3567792361 + 3120339600 = 59731^2 + 55860^2 .

It is not a de Polignac number, because 6688131961 - 2³ = 6688131953 is a prime.

It is a super-2 number, since 2×6688131961² = 89462218255499411042, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6688131941) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 4006435 + ... + 4008103.

Almost surely, 2^6688131961 is an apocalyptic number.

6688131961 is the 81781-st square number.

6688131961 is the 40891-st centered octagonal number.

It is an amenable number.

6688131961 is a deficient number, since it is larger than the sum of its proper divisors (1118902070).

6688131961 is an frugal number, since it uses more digits than its factorization.

6688131961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3366 (or 1676 counting only the distinct ones).

The product of its digits is 373248, while the sum is 49.

The cubic root of 6688131961 is about 1884.0898552121.

Multiplying 6688131961 by its sum of digits (49), we get a square (327718466089 = 572467²).

6688131961 divided by its sum of digits (49) gives a square (136492489 = 11683²).

The spelling of 6688131961 in words is "six billion, six hundred eighty-eight million, one hundred thirty-one thousand, nine hundred sixty-one".