21018881 has 16 divisors (see below), whose sum is σ = 23654400. Its totient is φ = 18543168.

The previous prime is 21018869. The next prime is 21018929. The reversal of 21018881 is 18881012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21018881 is a prime.

It is a super-2 number, since 2×21018881² = 883586716984322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21018821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47660 + ... + 48098.

It is an arithmetic number, because the mean of its divisors is an integer number (1478400).

Almost surely, 2^21018881 is an apocalyptic number.

It is an amenable number.

21018881 is a deficient number, since it is larger than the sum of its proper divisors (2635519).

21018881 is a wasteful number, since it uses less digits than its factorization.

21018881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 608.

The product of its (nonzero) digits is 1024, while the sum is 29.

The square root of 21018881 is about 4584.6353181033. The cubic root of 21018881 is about 275.9750773897.

Adding to 21018881 its reverse (18881012), we get a palindrome (39899893).

It can be divided in two parts, 210 and 18881, that added together give a palindrome (19091).

The spelling of 21018881 in words is "twenty-one million, eighteen thousand, eight hundred eighty-one".