1251721 has 2 divisors, whose sum is σ = 1251722. Its totient is φ = 1251720.

The previous prime is 1251713. The next prime is 1251743. The reversal of 1251721 is 1271521.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 705600 + 546121 = 840^2 + 739^2 .

It is an emirp because it is prime and its reverse (1271521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1251721 - 2³ = 1251713 is a prime.

1251721 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (1251791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 625860 + 625861.

It is an arithmetic number, because the mean of its divisors is an integer number (625861).

2^1251721 is an apocalyptic number.

It is an amenable number.

1251721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1251721 is an equidigital number, since it uses as much as digits as its factorization.

1251721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 140, while the sum is 19.

The square root of 1251721 is about 1118.8033786148. The cubic root of 1251721 is about 107.7711489253.

The spelling of 1251721 in words is "one million, two hundred fifty-one thousand, seven hundred twenty-one".