1640560421 has 4 divisors (see below), whose sum is σ = 1697131500. Its totient is φ = 1583989344.

The previous prime is 1640560403. The next prime is 1640560433. The reversal of 1640560421 is 1240650461.

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 490401025 + 1150159396 = 22145^2 + 33914^2 .

It is a cyclic number.

It is not a de Polignac number, because 1640560421 - 2³⁰ = 566818597 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 56571049 = 1640560421 / (1 + 6 + 4 + 0 + 5 + 6 + 0 + 4 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1640560451) 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, 28285496 + ... + 28285553.

It is an arithmetic number, because the mean of its divisors is an integer number (424282875).

Almost surely, 2^1640560421 is an apocalyptic number.

It is an amenable number.

1640560421 is a deficient number, since it is larger than the sum of its proper divisors (56571079).

1640560421 is an equidigital number, since it uses as much as digits as its factorization.

1640560421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56571078.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 1640560421 is about 40503.8321767213. The cubic root of 1640560421 is about 1179.4080198813.

The spelling of 1640560421 in words is "one billion, six hundred forty million, five hundred sixty thousand, four hundred twenty-one".