1390721 has 4 divisors (see below), whose sum is σ = 1393200. Its totient is φ = 1388244.

The previous prime is 1390709. The next prime is 1390729. The reversal of 1390721 is 1270931.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1270931 = 857 ⋅1483.

It is a cyclic number.

It is not a de Polignac number, because 1390721 - 2¹⁰ = 1389697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1390729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50 + ... + 1668.

It is an arithmetic number, because the mean of its divisors is an integer number (348300).

2^1390721 is an apocalyptic number.

It is an amenable number.

1390721 is a deficient number, since it is larger than the sum of its proper divisors (2479).

1390721 is an equidigital number, since it uses as much as digits as its factorization.

1390721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2478.

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

The square root of 1390721 is about 1179.2883447232. The cubic root of 1390721 is about 111.6211958131.

The spelling of 1390721 in words is "one million, three hundred ninety thousand, seven hundred twenty-one".