172042721 has 2 divisors, whose sum is σ = 172042722. Its totient is φ = 172042720.

The previous prime is 172042697. The next prime is 172042723. The reversal of 172042721 is 127240271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 171898321 + 144400 = 13111^2 + 380^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-172042721 is a prime.

Together with 172042723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (172042723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86021360 + 86021361.

It is an arithmetic number, because the mean of its divisors is an integer number (86021361).

Almost surely, 2^172042721 is an apocalyptic number.

It is an amenable number.

172042721 is a deficient number, since it is larger than the sum of its proper divisors (1).

172042721 is an equidigital number, since it uses as much as digits as its factorization.

172042721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1568, while the sum is 26.

The square root of 172042721 is about 13116.5056703377. The cubic root of 172042721 is about 556.1758162906.

Adding to 172042721 its reverse (127240271), we get a palindrome (299282992).

The spelling of 172042721 in words is "one hundred seventy-two million, forty-two thousand, seven hundred twenty-one".