20121661 has 4 divisors (see below), whose sum is σ = 22996192. Its totient is φ = 17247132.

The previous prime is 20121653. The next prime is 20121667. The reversal of 20121661 is 16612102.

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 not a de Polignac number, because 20121661 - 2³ = 20121653 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 (20121667) 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, 1437255 + ... + 1437268.

It is an arithmetic number, because the mean of its divisors is an integer number (5749048).

Almost surely, 2^20121661 is an apocalyptic number.

It is an amenable number.

20121661 is a deficient number, since it is larger than the sum of its proper divisors (2874531).

20121661 is an equidigital number, since it uses as much as digits as its factorization.

20121661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2874530.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 20121661 is about 4485.7174454038. The cubic root of 20121661 is about 271.9910473192.

Adding to 20121661 its reverse (16612102), we get a palindrome (36733763).

The spelling of 20121661 in words is "twenty million, one hundred twenty-one thousand, six hundred sixty-one".