20897881 has 8 divisors (see below), whose sum is σ = 21224520. Its totient is φ = 20573952.

The previous prime is 20897873. The next prime is 20897909. The reversal of 20897881 is 18879802.

It can be written as a sum of positive squares in 4 ways, for example, as 1713481 + 19184400 = 1309^2 + 4380^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20897881 - 2³ = 20897873 is a prime.

It is a super-2 number, since 2×20897881² = 873442860580322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20897801) 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 7 ways as a sum of consecutive naturals, for example, 19015 + ... + 20083.

It is an arithmetic number, because the mean of its divisors is an integer number (2653065).

Almost surely, 2^20897881 is an apocalyptic number.

It is an amenable number.

20897881 is a deficient number, since it is larger than the sum of its proper divisors (326639).

20897881 is a wasteful number, since it uses less digits than its factorization.

20897881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1355.

The product of its (nonzero) digits is 64512, while the sum is 43.

The square root of 20897881 is about 4571.4200200813. The cubic root of 20897881 is about 275.4444866920. Note that the first 4 decimals are identical.

It can be divided in two parts, 208 and 97881, that added together give a palindrome (98089).

The spelling of 20897881 in words is "twenty million, eight hundred ninety-seven thousand, eight hundred eighty-one".