66656421 has 12 divisors (see below), whose sum is σ = 103687948. Its totient is φ = 41019264.

The previous prime is 66656419. The next prime is 66656423. The reversal of 66656421 is 12465666.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (66656419) and next prime (66656423).

It can be written as a sum of positive squares in 2 ways, for example, as 41796225 + 24860196 = 6465^2 + 4986^2 .

It is not a de Polignac number, because 66656421 - 2¹ = 66656419 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66656423) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 284740 + ... + 284973.

Almost surely, 2^66656421 is an apocalyptic number.

It is an amenable number.

66656421 is a deficient number, since it is larger than the sum of its proper divisors (37031527).

66656421 is a wasteful number, since it uses less digits than its factorization.

66656421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 569732 (or 569729 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 66656421 is about 8164.3383687841. The cubic root of 66656421 is about 405.4593599026.

The spelling of 66656421 in words is "sixty-six million, six hundred fifty-six thousand, four hundred twenty-one".