66561431 has 8 divisors (see below), whose sum is σ = 67797744. Its totient is φ = 65329920.

The previous prime is 66561413. The next prime is 66561437. The reversal of 66561431 is 13416566.

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

It is a cyclic number.

It is not a de Polignac number, because 66561431 - 2¹⁰ = 66560407 is a prime.

It is a super-2 number, since 2×66561431² = 8860848193535522, which contains 22 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 (66561437) 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, 38375 + ... + 40071.

It is an arithmetic number, because the mean of its divisors is an integer number (8474718).

Almost surely, 2^66561431 is an apocalyptic number.

66561431 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

66561431 is a deficient number, since it is larger than the sum of its proper divisors (1236313).

66561431 is a wasteful number, since it uses less digits than its factorization.

66561431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2401.

The product of its digits is 12960, while the sum is 32.

The square root of 66561431 is about 8158.5189219613. The cubic root of 66561431 is about 405.2666658164.

Adding to 66561431 its reverse (13416566), we get a palindrome (79977997).

The spelling of 66561431 in words is "sixty-six million, five hundred sixty-one thousand, four hundred thirty-one".