1648211381 has 4 divisors (see below), whose sum is σ = 1666730700. Its totient is φ = 1629692064.

The previous prime is 1648211351. The next prime is 1648211393. The reversal of 1648211381 is 1831128461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 284091025 + 1364120356 = 16855^2 + 36934^2 .

It is a cyclic number.

It is not a de Polignac number, because 1648211381 - 2¹⁰ = 1648210357 is a prime.

It is a super-2 number, since 2×1648211381² = 5433201512915854322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1648211321) 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, 9259526 + ... + 9259703.

It is an arithmetic number, because the mean of its divisors is an integer number (416682675).

Almost surely, 2^1648211381 is an apocalyptic number.

It is an amenable number.

1648211381 is a deficient number, since it is larger than the sum of its proper divisors (18519319).

1648211381 is an equidigital number, since it uses as much as digits as its factorization.

1648211381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18519318.

The product of its digits is 9216, while the sum is 35.

The square root of 1648211381 is about 40598.1696754915. The cubic root of 1648211381 is about 1181.2386163307.

The spelling of 1648211381 in words is "one billion, six hundred forty-eight million, two hundred eleven thousand, three hundred eighty-one".