1648634991 has 4 divisors (see below), whose sum is σ = 2198179992. Its totient is φ = 1099089992.

The previous prime is 1648634987. The next prime is 1648635029. The reversal of 1648634991 is 1994368461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1994368461 = 3 ⋅664789487.

It is a cyclic number.

It is not a de Polignac number, because 1648634991 - 2² = 1648634987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1648634951) 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, 274772496 + ... + 274772501.

It is an arithmetic number, because the mean of its divisors is an integer number (549544998).

Almost surely, 2^1648634991 is an apocalyptic number.

1648634991 is a deficient number, since it is larger than the sum of its proper divisors (549545001).

1648634991 is an equidigital number, since it uses as much as digits as its factorization.

1648634991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549545000.

The product of its digits is 1119744, while the sum is 51.

The square root of 1648634991 is about 40603.3864474381. The cubic root of 1648634991 is about 1181.3398051373.

The spelling of 1648634991 in words is "one billion, six hundred forty-eight million, six hundred thirty-four thousand, nine hundred ninety-one".