19797661 has 4 divisors (see below), whose sum is σ = 21320572. Its totient is φ = 18274752.

The previous prime is 19797619. The next prime is 19797667. The reversal of 19797661 is 16679791.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16679791 = 857 ⋅19463.

It can be written as a sum of positive squares in 2 ways, for example, as 5433561 + 14364100 = 2331^2 + 3790^2 .

It is a cyclic number.

It is not a de Polignac number, because 19797661 - 2⁹ = 19797149 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19797667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 761436 + ... + 761461.

It is an arithmetic number, because the mean of its divisors is an integer number (5330143).

Almost surely, 2^19797661 is an apocalyptic number.

It is an amenable number.

19797661 is a deficient number, since it is larger than the sum of its proper divisors (1522911).

19797661 is a wasteful number, since it uses less digits than its factorization.

19797661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1522910.

The product of its digits is 142884, while the sum is 46.

The square root of 19797661 is about 4449.4562589152. The cubic root of 19797661 is about 270.5232696375.

The spelling of 19797661 in words is "nineteen million, seven hundred ninety-seven thousand, six hundred sixty-one".