1908721 has 4 divisors (see below), whose sum is σ = 2009200. Its totient is φ = 1808244.

The previous prime is 1908713. The next prime is 1908737. The reversal of 1908721 is 1278091.

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: 1278091 = 37 ⋅34543.

It is a cyclic number.

It is not a de Polignac number, because 1908721 - 2³ = 1908713 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1908721.

It is not an unprimeable number, because it can be changed into a prime (1908761) 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, 50211 + ... + 50248.

It is an arithmetic number, because the mean of its divisors is an integer number (502300).

2^1908721 is an apocalyptic number.

It is an amenable number.

1908721 is a deficient number, since it is larger than the sum of its proper divisors (100479).

1908721 is a wasteful number, since it uses less digits than its factorization.

1908721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100478.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 1908721 is about 1381.5646926583. The cubic root of 1908721 is about 124.0454438015.

It can be divided in two parts, 190 and 8721, that added together give a triangular number (8911 = T₁₃₃).

The spelling of 1908721 in words is "one million, nine hundred eight thousand, seven hundred twenty-one".