21998081 has 8 divisors (see below), whose sum is σ = 25182144. Its totient is φ = 18824400.

The previous prime is 21998033. The next prime is 21998107. The reversal of 21998081 is 18089912.

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

It is not a de Polignac number, because 21998081 - 2¹⁸ = 21735937 is a prime.

It is a super-2 number, since 2×21998081² = 967831135365122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21998381) 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 7 ways as a sum of consecutive naturals, for example, 2666 + ... + 7148.

It is an arithmetic number, because the mean of its divisors is an integer number (3147768).

Almost surely, 2^21998081 is an apocalyptic number.

It is an amenable number.

21998081 is a deficient number, since it is larger than the sum of its proper divisors (3184063).

21998081 is an equidigital number, since it uses as much as digits as its factorization.

21998081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5191.

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 21998081 is about 4690.2111892750. The cubic root of 21998081 is about 280.1957856870.

The spelling of 21998081 in words is "twenty-one million, nine hundred ninety-eight thousand, eighty-one".