1971931661 has 8 divisors (see below), whose sum is σ = 2258067840. Its totient is φ = 1686903408.

The previous prime is 1971931651. The next prime is 1971931673. The reversal of 1971931661 is 1661391791.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1971931661 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1971931651) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 273161 + ... + 280286.

It is an arithmetic number, because the mean of its divisors is an integer number (282258480).

Almost surely, 2^1971931661 is an apocalyptic number.

It is an amenable number.

1971931661 is a deficient number, since it is larger than the sum of its proper divisors (286136179).

1971931661 is an equidigital number, since it uses as much as digits as its factorization.

1971931661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 553963.

The product of its digits is 61236, while the sum is 44.

The square root of 1971931661 is about 44406.4371572411. The cubic root of 1971931661 is about 1253.9992786503. Note that the first 3 decimals are identical.

The spelling of 1971931661 in words is "one billion, nine hundred seventy-one million, nine hundred thirty-one thousand, six hundred sixty-one".