1563721 has 4 divisors (see below), whose sum is σ = 1571344. Its totient is φ = 1556100.

The previous prime is 1563707. The next prime is 1563739. The reversal of 1563721 is 1273651.

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 not a de Polignac number, because 1563721 - 2⁵ = 1563689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1563791) 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, 3495 + ... + 3916.

It is an arithmetic number, because the mean of its divisors is an integer number (392836).

2^1563721 is an apocalyptic number.

It is an amenable number.

1563721 is a deficient number, since it is larger than the sum of its proper divisors (7623).

1563721 is an equidigital number, since it uses as much as digits as its factorization.

1563721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7622.

The product of its digits is 1260, while the sum is 25.

The square root of 1563721 is about 1250.4883046234. The cubic root of 1563721 is about 116.0699389969.

It can be divided in two parts, 15 and 63721, that added together give a palindrome (63736).

The spelling of 1563721 in words is "one million, five hundred sixty-three thousand, seven hundred twenty-one".