1664530621 has 4 divisors (see below), whose sum is σ = 1792571452. Its totient is φ = 1536489792.

The previous prime is 1664530591. The next prime is 1664530633. The reversal of 1664530621 is 1260354661.

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 989102500 + 675428121 = 31450^2 + 25989^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664530621 - 2⁵ = 1664530589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1664530921) 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, 64020396 + ... + 64020421.

It is an arithmetic number, because the mean of its divisors is an integer number (448142863).

Almost surely, 2^1664530621 is an apocalyptic number.

It is an amenable number.

1664530621 is a deficient number, since it is larger than the sum of its proper divisors (128040831).

1664530621 is a wasteful number, since it uses less digits than its factorization.

1664530621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128040830.

The product of its (nonzero) digits is 25920, while the sum is 34.

The square root of 1664530621 is about 40798.6595490587. The cubic root of 1664530621 is about 1185.1243725204.

The spelling of 1664530621 in words is "one billion, six hundred sixty-four million, five hundred thirty thousand, six hundred twenty-one".