42720221 has 2 divisors, whose sum is σ = 42720222. Its totient is φ = 42720220.

The previous prime is 42720217. The next prime is 42720233. The reversal of 42720221 is 12202724.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 37027225 + 5692996 = 6085^2 + 2386^2 .

It is a cyclic number.

It is not a de Polignac number, because 42720221 - 2² = 42720217 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 42720193 and 42720202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42720241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21360110 + 21360111.

It is an arithmetic number, because the mean of its divisors is an integer number (21360111).

Almost surely, 2^42720221 is an apocalyptic number.

It is an amenable number.

42720221 is a deficient number, since it is larger than the sum of its proper divisors (1).

42720221 is an equidigital number, since it uses as much as digits as its factorization.

42720221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 42720221 is about 6536.0707615509. The cubic root of 42720221 is about 349.5783248287.

Adding to 42720221 its reverse (12202724), we get a palindrome (54922945).

The spelling of 42720221 in words is "forty-two million, seven hundred twenty thousand, two hundred twenty-one".