655601621 has 2 divisors, whose sum is σ = 655601622. Its totient is φ = 655601620.

The previous prime is 655601599. The next prime is 655601623. The reversal of 655601621 is 126106556.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 590976100 + 64625521 = 24310^2 + 8039^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-655601621 is a prime.

Together with 655601623, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_34069370 and since 655601621 and 34069370 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (655601623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 327800810 + 327800811.

It is an arithmetic number, because the mean of its divisors is an integer number (327800811).

Almost surely, 2^655601621 is an apocalyptic number.

It is an amenable number.

655601621 is a deficient number, since it is larger than the sum of its proper divisors (1).

655601621 is an equidigital number, since it uses as much as digits as its factorization.

655601621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 655601621 is about 25604.7187252662. The cubic root of 655601621 is about 868.7203722898.

The spelling of 655601621 in words is "six hundred fifty-five million, six hundred one thousand, six hundred twenty-one".