66561401 has 8 divisors (see below), whose sum is σ = 67267200. Its totient is φ = 65859120.

The previous prime is 66561373. The next prime is 66561403. The reversal of 66561401 is 10416566.

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 66561401 - 2⁶ = 66561337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66561403) 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, 53456 + ... + 54686.

It is an arithmetic number, because the mean of its divisors is an integer number (8408400).

Almost surely, 2^66561401 is an apocalyptic number.

It is an amenable number.

66561401 is a deficient number, since it is larger than the sum of its proper divisors (705799).

66561401 is a wasteful number, since it uses less digits than its factorization.

66561401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1759.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 66561401 is about 8158.5170833921. The cubic root of 66561401 is about 405.2666049302.

Adding to 66561401 its reverse (10416566), we get a palindrome (76977967).

The spelling of 66561401 in words is "sixty-six million, five hundred sixty-one thousand, four hundred one".