1564380721 has 4 divisors (see below), whose sum is σ = 1600761712. Its totient is φ = 1527999732.

The previous prime is 1564380677. The next prime is 1564380733. The reversal of 1564380721 is 1270834651.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1564380721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1564380781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18190431 + ... + 18190516.

It is an arithmetic number, because the mean of its divisors is an integer number (400190428).

Almost surely, 2^1564380721 is an apocalyptic number.

It is an amenable number.

1564380721 is a deficient number, since it is larger than the sum of its proper divisors (36380991).

1564380721 is an equidigital number, since it uses as much as digits as its factorization.

1564380721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36380990.

The product of its (nonzero) digits is 40320, while the sum is 37.

The square root of 1564380721 is about 39552.2530458127. The cubic root of 1564380721 is about 1160.8625968547.

The spelling of 1564380721 in words is "one billion, five hundred sixty-four million, three hundred eighty thousand, seven hundred twenty-one".