20787121 has 4 divisors (see below), whose sum is σ = 21881200. Its totient is φ = 19693044.

The previous prime is 20787119. The next prime is 20787127. The reversal of 20787121 is 12178702.

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: 12178702 = 2 ⋅6089351.

It is not a de Polignac number, because 20787121 - 2¹ = 20787119 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20787121.

It is not an unprimeable number, because it can be changed into a prime (20787127) 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, 547011 + ... + 547048.

It is an arithmetic number, because the mean of its divisors is an integer number (5470300).

Almost surely, 2^20787121 is an apocalyptic number.

It is an amenable number.

20787121 is a deficient number, since it is larger than the sum of its proper divisors (1094079).

20787121 is a wasteful number, since it uses less digits than its factorization.

20787121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1094078.

The product of its (nonzero) digits is 1568, while the sum is 28.

The square root of 20787121 is about 4559.2895279857. The cubic root of 20787121 is about 274.9570004394.

The spelling of 20787121 in words is "twenty million, seven hundred eighty-seven thousand, one hundred twenty-one".