156721009 has 2 divisors, whose sum is σ = 156721010. Its totient is φ = 156721008.

The previous prime is 156721007. The next prime is 156721043. The reversal of 156721009 is 900127651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 156125025 + 595984 = 12495^2 + 772^2 .

It is a cyclic number.

It is not a de Polignac number, because 156721009 - 2¹ = 156721007 is a prime.

It is a super-2 number, since 2×156721009² = 49122949323956162, which contains 22 as substring.

Together with 156721007, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (156721001) 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, 78360504 + 78360505.

It is an arithmetic number, because the mean of its divisors is an integer number (78360505).

Almost surely, 2^156721009 is an apocalyptic number.

It is an amenable number.

156721009 is a deficient number, since it is larger than the sum of its proper divisors (1).

156721009 is an equidigital number, since it uses as much as digits as its factorization.

156721009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3780, while the sum is 31.

The square root of 156721009 is about 12518.8261829934. The cubic root of 156721009 is about 539.1493339398.

The spelling of 156721009 in words is "one hundred fifty-six million, seven hundred twenty-one thousand, nine".