21898081 has 4 divisors (see below), whose sum is σ = 21911472. Its totient is φ = 21884692.

The previous prime is 21898067. The next prime is 21898087. The reversal of 21898081 is 18089812.

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 a cyclic number.

It is not a de Polignac number, because 21898081 - 2⁹ = 21897569 is a prime.

It is a super-2 number, since 2×21898081² = 959051902965122, which contains 22 as substring.

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 21898081.

It is not an unprimeable number, because it can be changed into a prime (21898087) 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, 3835 + ... + 7648.

It is an arithmetic number, because the mean of its divisors is an integer number (5477868).

Almost surely, 2^21898081 is an apocalyptic number.

It is an amenable number.

21898081 is a deficient number, since it is larger than the sum of its proper divisors (13391).

21898081 is a wasteful number, since it uses less digits than its factorization.

21898081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13390.

The product of its (nonzero) digits is 9216, while the sum is 37.

The square root of 21898081 is about 4679.5385456261. The cubic root of 21898081 is about 279.7705646002.

The spelling of 21898081 in words is "twenty-one million, eight hundred ninety-eight thousand, eighty-one".