66616421 has 4 divisors (see below), whose sum is σ = 70535052. Its totient is φ = 62697792.

The previous prime is 66616409. The next prime is 66616439. The reversal of 66616421 is 12461666.

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

It can be written as a sum of positive squares in 2 ways, for example, as 57532225 + 9084196 = 7585^2 + 3014^2 .

It is a cyclic number.

It is not a de Polignac number, because 66616421 - 2⁶ = 66616357 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 (66616471) 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, 1959290 + ... + 1959323.

It is an arithmetic number, because the mean of its divisors is an integer number (17633763).

Almost surely, 2^66616421 is an apocalyptic number.

It is an amenable number.

66616421 is a deficient number, since it is larger than the sum of its proper divisors (3918631).

66616421 is a wasteful number, since it uses less digits than its factorization.

66616421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3918630.

The product of its digits is 10368, while the sum is 32.

The square root of 66616421 is about 8161.8883231762. Note that the first 3 decimals coincide. The cubic root of 66616421 is about 405.3782393373.

The spelling of 66616421 in words is "sixty-six million, six hundred sixteen thousand, four hundred twenty-one".