19964561 has 4 divisors (see below), whose sum is σ = 20245824. Its totient is φ = 19683300.

The previous prime is 19964537. The next prime is 19964563. The reversal of 19964561 is 16546991.

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: 16546991 = 1181 ⋅14011.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19964561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19964563) 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, 140525 + ... + 140666.

It is an arithmetic number, because the mean of its divisors is an integer number (5061456).

Almost surely, 2^19964561 is an apocalyptic number.

It is an amenable number.

19964561 is a deficient number, since it is larger than the sum of its proper divisors (281263).

19964561 is an equidigital number, since it uses as much as digits as its factorization.

19964561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 281262.

The product of its digits is 58320, while the sum is 41.

The square root of 19964561 is about 4468.1719975847. The cubic root of 19964561 is about 271.2813397924.

The spelling of 19964561 in words is "nineteen million, nine hundred sixty-four thousand, five hundred sixty-one".