66562721 has 8 divisors (see below), whose sum is σ = 68296200. Its totient is φ = 64834560.

The previous prime is 66562697. The next prime is 66562723. The reversal of 66562721 is 12726566.

It can be written as a sum of positive squares in 4 ways, for example, as 6964321 + 59598400 = 2639^2 + 7720^2 .

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 66562721 - 2¹⁰ = 66561697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66562723) 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, 40565 + ... + 42173.

It is an arithmetic number, because the mean of its divisors is an integer number (8537025).

Almost surely, 2^66562721 is an apocalyptic number.

It is an amenable number.

66562721 is a deficient number, since it is larger than the sum of its proper divisors (1733479).

66562721 is a wasteful number, since it uses less digits than its factorization.

66562721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2659.

The product of its digits is 30240, while the sum is 35.

The square root of 66562721 is about 8158.5979800453. The cubic root of 66562721 is about 405.2692839022.

The spelling of 66562721 in words is "sixty-six million, five hundred sixty-two thousand, seven hundred twenty-one".