139721 has 2 divisors, whose sum is σ = 139722. Its totient is φ = 139720.

The previous prime is 139709. The next prime is 139729. The reversal of 139721 is 127931.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 132496 + 7225 = 364^2 + 85^2 .

It is an emirp because it is prime and its reverse (127931) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-139721 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (139729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69860 + 69861.

It is an arithmetic number, because the mean of its divisors is an integer number (69861).

2¹³⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

139721 is a deficient number, since it is larger than the sum of its proper divisors (1).

139721 is an equidigital number, since it uses as much as digits as its factorization.

139721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 378, while the sum is 23.

The square root of 139721 is about 373.7927233107. The cubic root of 139721 is about 51.8904250834.

The spelling of 139721 in words is "one hundred thirty-nine thousand, seven hundred twenty-one".