1378721 has 2 divisors, whose sum is σ = 1378722. Its totient is φ = 1378720.

The previous prime is 1378703. The next prime is 1378733. The reversal of 1378721 is 1278731.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1234321 + 144400 = 1111^2 + 380^2 .

It is a cyclic number.

It is not a de Polignac number, because 1378721 - 2¹⁴ = 1362337 is a prime.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (1374721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 689360 + 689361.

It is an arithmetic number, because the mean of its divisors is an integer number (689361).

2^1378721 is an apocalyptic number.

It is an amenable number.

1378721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1378721 is an equidigital number, since it uses as much as digits as its factorization.

1378721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2352, while the sum is 29.

The square root of 1378721 is about 1174.1895077031. The cubic root of 1378721 is about 111.2992224216.

The spelling of 1378721 in words is "one million, three hundred seventy-eight thousand, seven hundred twenty-one".