1540608721 has 4 divisors (see below), whose sum is σ = 1547336500. Its totient is φ = 1533880944.

The previous prime is 1540608689. The next prime is 1540608739. The reversal of 1540608721 is 1278060451.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1199652496 + 340956225 = 34636^2 + 18465^2 .

It is a cyclic number.

It is not a de Polignac number, because 1540608721 - 2⁵ = 1540608689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1540608781) 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, 3363546 + ... + 3364003.

It is an arithmetic number, because the mean of its divisors is an integer number (386834125).

Almost surely, 2^1540608721 is an apocalyptic number.

It is an amenable number.

1540608721 is a deficient number, since it is larger than the sum of its proper divisors (6727779).

1540608721 is an equidigital number, since it uses as much as digits as its factorization.

1540608721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6727778.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 1540608721 is about 39250.5887981314. The cubic root of 1540608721 is about 1154.9524841931.

The spelling of 1540608721 in words is "one billion, five hundred forty million, six hundred eight thousand, seven hundred twenty-one".