42765721 has 2 divisors, whose sum is σ = 42765722. Its totient is φ = 42765720.

The previous prime is 42765719. The next prime is 42765731. The reversal of 42765721 is 12756724.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 42575625 + 190096 = 6525^2 + 436^2 .

It is a cyclic number.

It is not a de Polignac number, because 42765721 - 2¹ = 42765719 is a prime.

Together with 42765719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (42765731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21382860 + 21382861.

It is an arithmetic number, because the mean of its divisors is an integer number (21382861).

Almost surely, 2^42765721 is an apocalyptic number.

It is an amenable number.

42765721 is a deficient number, since it is larger than the sum of its proper divisors (1).

42765721 is an equidigital number, since it uses as much as digits as its factorization.

42765721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23520, while the sum is 34.

The square root of 42765721 is about 6539.5505197223. The cubic root of 42765721 is about 349.7023891852.

The spelling of 42765721 in words is "forty-two million, seven hundred sixty-five thousand, seven hundred twenty-one".