1640974821 has 4 divisors (see below), whose sum is σ = 2187966432. Its totient is φ = 1093983212.

The previous prime is 1640974789. The next prime is 1640974837. The reversal of 1640974821 is 1284790461.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1640974821 - 2⁵ = 1640974789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640974421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273495801 + ... + 273495806.

It is an arithmetic number, because the mean of its divisors is an integer number (546991608).

Almost surely, 2^1640974821 is an apocalyptic number.

It is an amenable number.

1640974821 is a deficient number, since it is larger than the sum of its proper divisors (546991611).

1640974821 is an equidigital number, since it uses as much as digits as its factorization.

1640974821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546991610.

The product of its (nonzero) digits is 96768, while the sum is 42.

The square root of 1640974821 is about 40508.9474190579. The cubic root of 1640974821 is about 1179.5073163435.

The spelling of 1640974821 in words is "one billion, six hundred forty million, nine hundred seventy-four thousand, eight hundred twenty-one".