1020505721 has 8 divisors (see below), whose sum is σ = 1027518024. Its totient is φ = 1013506560.

The previous prime is 1020505711. The next prime is 1020505729. The reversal of 1020505721 is 1275050201.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 19669225 + 1000836496 = 4435^2 + 31636^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1020505721 - 2⁶ = 1020505657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1020505729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 190601 + ... + 195881.

It is an arithmetic number, because the mean of its divisors is an integer number (128439753).

Almost surely, 2^1020505721 is an apocalyptic number.

It is an amenable number.

1020505721 is a deficient number, since it is larger than the sum of its proper divisors (7012303).

1020505721 is a wasteful number, since it uses less digits than its factorization.

1020505721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6571.

The product of its (nonzero) digits is 700, while the sum is 23.

The square root of 1020505721 is about 31945.3552335860. The cubic root of 1020505721 is about 1006.7890448978.

Adding to 1020505721 its reverse (1275050201), we get a palindrome (2295555922).

The spelling of 1020505721 in words is "one billion, twenty million, five hundred five thousand, seven hundred twenty-one".