1610720721 has 40 divisors (see below), whose sum is σ = 2459894184. Its totient is φ = 1049967360.

The previous prime is 1610720719. The next prime is 1610720729. The reversal of 1610720721 is 1270270161.

1610720721 is a `hidden beast` number, since 1 + 610 + 7 + 20 + 7 + 21 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 504227025 + 1106493696 = 22455^2 + 33264^2 .

It is not a de Polignac number, because 1610720721 - 2¹ = 1610720719 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1610720729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1961491 + ... + 1962311.

Almost surely, 2^1610720721 is an apocalyptic number.

It is an amenable number.

1610720721 is a deficient number, since it is larger than the sum of its proper divisors (849173463).

1610720721 is an equidigital number, since it uses as much as digits as its factorization.

1610720721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1343 (or 1334 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 27.

The square root of 1610720721 is about 40133.7852812316. The cubic root of 1610720721 is about 1172.2135805800.

Adding to 1610720721 its reverse (1270270161), we get a palindrome (2880990882).

The spelling of 1610720721 in words is "one billion, six hundred ten million, seven hundred twenty thousand, seven hundred twenty-one".