15664164421 has 4 divisors (see below), whose sum is σ = 16345215072. Its totient is φ = 14983113772.

The previous prime is 15664164409. The next prime is 15664164491. The reversal of 15664164421 is 12446146651.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12446146651 = 61 ⋅204035191.

It is a cyclic number.

It is not a de Polignac number, because 15664164421 - 2²¹ = 15662067269 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15664164401) 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, 340525291 + ... + 340525336.

It is an arithmetic number, because the mean of its divisors is an integer number (4086303768).

Almost surely, 2^15664164421 is an apocalyptic number.

It is an amenable number.

15664164421 is a deficient number, since it is larger than the sum of its proper divisors (681050651).

15664164421 is an equidigital number, since it uses as much as digits as its factorization.

15664164421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 681050650.

The product of its digits is 138240, while the sum is 40.

The spelling of 15664164421 in words is "fifteen billion, six hundred sixty-four million, one hundred sixty-four thousand, four hundred twenty-one".