65551561 has 4 divisors (see below), whose sum is σ = 65765392. Its totient is φ = 65337732.

The previous prime is 65551559. The next prime is 65551567. The reversal of 65551561 is 16515556.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 65551561 - 2¹ = 65551559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (65551567) 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, 106455 + ... + 107068.

It is an arithmetic number, because the mean of its divisors is an integer number (16441348).

Almost surely, 2^65551561 is an apocalyptic number.

It is an amenable number.

65551561 is a deficient number, since it is larger than the sum of its proper divisors (213831).

65551561 is a wasteful number, since it uses less digits than its factorization.

65551561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213830.

The product of its digits is 22500, while the sum is 34.

The square root of 65551561 is about 8096.3918506950. The cubic root of 65551561 is about 403.2066436485.

The spelling of 65551561 in words is "sixty-five million, five hundred fifty-one thousand, five hundred sixty-one".