66720887 has 4 divisors (see below), whose sum is σ = 66818136. Its totient is φ = 66623640.

The previous prime is 66720751. The next prime is 66720889. The reversal of 66720887 is 78802766.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 66720887 - 2²⁰ = 65672311 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 (66720889) 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, 47588 + ... + 48969.

It is an arithmetic number, because the mean of its divisors is an integer number (16704534).

Almost surely, 2^66720887 is an apocalyptic number.

66720887 is a deficient number, since it is larger than the sum of its proper divisors (97249).

66720887 is an equidigital number, since it uses as much as digits as its factorization.

66720887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97248.

The product of its (nonzero) digits is 225792, while the sum is 44.

The square root of 66720887 is about 8168.2854382055. The cubic root of 66720887 is about 405.5900295903.

The spelling of 66720887 in words is "sixty-six million, seven hundred twenty thousand, eight hundred eighty-seven".