71553661 has 4 divisors (see below), whose sum is σ = 71574300. Its totient is φ = 71533024.

The previous prime is 71553659. The next prime is 71553689. The reversal of 71553661 is 16635517.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16635517 = 3943 ⋅4219.

It can be written as a sum of positive squares in 2 ways, for example, as 40081561 + 31472100 = 6331^2 + 5610^2 .

It is a cyclic number.

It is not a de Polignac number, because 71553661 - 2¹ = 71553659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71553761) 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, 3706 + ... + 12523.

It is an arithmetic number, because the mean of its divisors is an integer number (17893575).

Almost surely, 2^71553661 is an apocalyptic number.

It is an amenable number.

71553661 is a deficient number, since it is larger than the sum of its proper divisors (20639).

71553661 is a wasteful number, since it uses less digits than its factorization.

71553661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20638.

The product of its digits is 18900, while the sum is 34.

The square root of 71553661 is about 8458.9397089706. The cubic root of 71553661 is about 415.1553316050.

It can be divided in two parts, 7155 and 3661, that added together give a square (10816 = 104²).

The spelling of 71553661 in words is "seventy-one million, five hundred fifty-three thousand, six hundred sixty-one".