1545851721 has 4 divisors (see below), whose sum is σ = 2061135632. Its totient is φ = 1030567812.

The previous prime is 1545851717. The next prime is 1545851731. The reversal of 1545851721 is 1271585451.

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: 1271585451 = 3 ⋅423861817.

It is not a de Polignac number, because 1545851721 - 2² = 1545851717 is a prime.

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 1545851721.

It is not an unprimeable number, because it can be changed into a prime (1545851731) 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, 257641951 + ... + 257641956.

It is an arithmetic number, because the mean of its divisors is an integer number (515283908).

Almost surely, 2^1545851721 is an apocalyptic number.

It is an amenable number.

1545851721 is a deficient number, since it is larger than the sum of its proper divisors (515283911).

1545851721 is an equidigital number, since it uses as much as digits as its factorization.

1545851721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 515283910.

The product of its digits is 56000, while the sum is 39.

The square root of 1545851721 is about 39317.3208776997. The cubic root of 1545851721 is about 1156.2611789287.

The spelling of 1545851721 in words is "one billion, five hundred forty-five million, eight hundred fifty-one thousand, seven hundred twenty-one".