1491375721 has 32 divisors (see below), whose sum is σ = 1780732800. Its totient is φ = 1233792000.

The previous prime is 1491375689. The next prime is 1491375731. The reversal of 1491375721 is 1275731941.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1491375721 - 2⁵ = 1491375689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1491375731) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1460191 + ... + 1461211.

It is an arithmetic number, because the mean of its divisors is an integer number (55647900).

Almost surely, 2^1491375721 is an apocalyptic number.

1491375721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1491375721 is a deficient number, since it is larger than the sum of its proper divisors (289357079).

1491375721 is a wasteful number, since it uses less digits than its factorization.

1491375721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1321.

The product of its digits is 52920, while the sum is 40.

The square root of 1491375721 is about 38618.3340008344. The cubic root of 1491375721 is about 1142.5161723168.

The spelling of 1491375721 in words is "one billion, four hundred ninety-one million, three hundred seventy-five thousand, seven hundred twenty-one".