66635621 has 8 divisors (see below), whose sum is σ = 72178680. Its totient is φ = 61152192.

The previous prime is 66635609. The next prime is 66635633. The reversal of 66635621 is 12653666.

It is an interprime number because it is at equal distance from previous prime (66635609) and next prime (66635633).

It can be written as a sum of positive squares in 4 ways, for example, as 25867396 + 40768225 = 5086^2 + 6385^2 .

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 66635621 - 2¹⁰ = 66634597 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 (66635671) 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, 12566 + ... + 17063.

It is an arithmetic number, because the mean of its divisors is an integer number (9022335).

Almost surely, 2^66635621 is an apocalyptic number.

It is an amenable number.

66635621 is a deficient number, since it is larger than the sum of its proper divisors (5543059).

66635621 is a wasteful number, since it uses less digits than its factorization.

66635621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29815.

The product of its digits is 38880, while the sum is 35.

The square root of 66635621 is about 8163.0644368399. The cubic root of 66635621 is about 405.4171812601.

The spelling of 66635621 in words is "sixty-six million, six hundred thirty-five thousand, six hundred twenty-one".