20197661 has 4 divisors (see below), whose sum is σ = 22033824. Its totient is φ = 18361500.

The previous prime is 20197637. The next prime is 20197669. The reversal of 20197661 is 16679102.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20197661 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 (20197669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 918065 + ... + 918086.

It is an arithmetic number, because the mean of its divisors is an integer number (5508456).

Almost surely, 2^20197661 is an apocalyptic number.

It is an amenable number.

20197661 is a deficient number, since it is larger than the sum of its proper divisors (1836163).

20197661 is a wasteful number, since it uses less digits than its factorization.

20197661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1836162.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 20197661 is about 4494.1807929811. The cubic root of 20197661 is about 272.3330560085. Note that the first 3 decimals are identical.

The spelling of 20197661 in words is "twenty million, one hundred ninety-seven thousand, six hundred sixty-one".