71511661 has 8 divisors (see below), whose sum is σ = 77346360. Its totient is φ = 65724672.

The previous prime is 71511641. The next prime is 71511679. The reversal of 71511661 is 16611517.

It can be written as a sum of positive squares in 4 ways, for example, as 1705636 + 69806025 = 1306^2 + 8355^2 .

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

It is a de Polignac number, because none of the positive numbers 2^k-71511661 is a prime.

It is a super-2 number, since 2×71511661² = 10227835317957842, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71511641) 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 7 ways as a sum of consecutive naturals, for example, 8776 + ... + 14833.

It is an arithmetic number, because the mean of its divisors is an integer number (9668295).

Almost surely, 2^71511661 is an apocalyptic number.

It is an amenable number.

71511661 is a deficient number, since it is larger than the sum of its proper divisors (5834699).

71511661 is a wasteful number, since it uses less digits than its factorization.

71511661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23855.

The product of its digits is 1260, while the sum is 28.

The square root of 71511661 is about 8456.4567639171. The cubic root of 71511661 is about 415.0740875131.

It can be divided in two parts, 7151 and 1661, that multiplied together give a palindrome (11877811).

The spelling of 71511661 in words is "seventy-one million, five hundred eleven thousand, six hundred sixty-one".