42643661 has 2 divisors, whose sum is σ = 42643662. Its totient is φ = 42643660.

The previous prime is 42643637. The next prime is 42643663. The reversal of 42643661 is 16634624.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28249225 + 14394436 = 5315^2 + 3794^2 .

It is a cyclic number.

It is not a de Polignac number, because 42643661 - 2⁶ = 42643597 is a prime.

Together with 42643663, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42643663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21321830 + 21321831.

It is an arithmetic number, because the mean of its divisors is an integer number (21321831).

Almost surely, 2^42643661 is an apocalyptic number.

It is an amenable number.

42643661 is a deficient number, since it is larger than the sum of its proper divisors (1).

42643661 is an equidigital number, since it uses as much as digits as its factorization.

42643661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 32.

The square root of 42643661 is about 6530.2114054600. The cubic root of 42643661 is about 349.3693705377.

The spelling of 42643661 in words is "forty-two million, six hundred forty-three thousand, six hundred sixty-one".