1991409245 has 18 divisors (see below), whose sum is σ = 2780820126. Its totient is φ = 1365058800.

The previous prime is 1991409239. The next prime is 1991409271. The reversal of 1991409245 is 5429041991.

It can be written as a sum of positive squares in only one way, i.e., 1593127396 + 398281849 = 39914^2 + 19957^2 .

It is not a de Polignac number, because 1991409245 - 2⁴ = 1991409229 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1991409196 and 1991409205.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 697070 + ... + 699920.

It is an arithmetic number, because the mean of its divisors is an integer number (154490007).

Almost surely, 2^1991409245 is an apocalyptic number.

It is an amenable number.

1991409245 is a deficient number, since it is larger than the sum of its proper divisors (789410881).

1991409245 is an frugal number, since it uses more digits than its factorization.

1991409245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5721 (or 2863 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 44.

The square root of 1991409245 is about 44625.2086269633. The cubic root of 1991409245 is about 1258.1145153281.

The spelling of 1991409245 in words is "one billion, nine hundred ninety-one million, four hundred nine thousand, two hundred forty-five".