55666621 has 2 divisors, whose sum is σ = 55666622. Its totient is φ = 55666620.

The previous prime is 55666613. The next prime is 55666649. The reversal of 55666621 is 12666655.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55666521 + 100 = 7461^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 55666621 - 2³ = 55666613 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (55666021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27833310 + 27833311.

It is an arithmetic number, because the mean of its divisors is an integer number (27833311).

Almost surely, 2^55666621 is an apocalyptic number.

It is an amenable number.

55666621 is a deficient number, since it is larger than the sum of its proper divisors (1).

55666621 is an equidigital number, since it uses as much as digits as its factorization.

55666621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 64800, while the sum is 37.

The square root of 55666621 is about 7461.0067015115. The cubic root of 55666621 is about 381.8255213167.

The spelling of 55666621 in words is "fifty-five million, six hundred sixty-six thousand, six hundred twenty-one".