20661899 has 4 divisors (see below), whose sum is σ = 20697336. Its totient is φ = 20626464.

The previous prime is 20661881. The next prime is 20661913. The reversal of 20661899 is 99816602.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20661899 - 2⁸ = 20661643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20661869) 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, 16829 + ... + 18014.

It is an arithmetic number, because the mean of its divisors is an integer number (5174334).

Almost surely, 2^20661899 is an apocalyptic number.

20661899 is a deficient number, since it is larger than the sum of its proper divisors (35437).

20661899 is an equidigital number, since it uses as much as digits as its factorization.

20661899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35436.

The product of its (nonzero) digits is 46656, while the sum is 41.

The square root of 20661899 is about 4545.5361619945. The cubic root of 20661899 is about 274.4037727171.

The spelling of 20661899 in words is "twenty million, six hundred sixty-one thousand, eight hundred ninety-nine".