661091471 has 4 divisors (see below), whose sum is σ = 666941952. Its totient is φ = 655240992.

The previous prime is 661091467. The next prime is 661091477. The reversal of 661091471 is 174190166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 174190166 = 2 ⋅87095083.

It is a cyclic number.

It is not a de Polignac number, because 661091471 - 2² = 661091467 is a prime.

It is a super-3 number, since 3×661091471³ (a number of 27 digits) contains 333 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 (661091477) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2925071 + ... + 2925296.

It is an arithmetic number, because the mean of its divisors is an integer number (166735488).

Almost surely, 2^661091471 is an apocalyptic number.

661091471 is a deficient number, since it is larger than the sum of its proper divisors (5850481).

661091471 is a wasteful number, since it uses less digits than its factorization.

661091471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5850480.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 661091471 is about 25711.6991076047. The cubic root of 661091471 is about 871.1384536769.

The spelling of 661091471 in words is "six hundred sixty-one million, ninety-one thousand, four hundred seventy-one".