21981299 has 4 divisors (see below), whose sum is σ = 22492536. Its totient is φ = 21470064.

The previous prime is 21981283. The next prime is 21981301. The reversal of 21981299 is 99218912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21981299 - 2⁴ = 21981283 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21981229) 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, 255554 + ... + 255639.

It is an arithmetic number, because the mean of its divisors is an integer number (5623134).

Almost surely, 2^21981299 is an apocalyptic number.

21981299 is a deficient number, since it is larger than the sum of its proper divisors (511237).

21981299 is an equidigital number, since it uses as much as digits as its factorization.

21981299 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 511236.

The product of its digits is 23328, while the sum is 41.

The square root of 21981299 is about 4688.4218026965. The cubic root of 21981299 is about 280.1245151985.

It can be divided in two parts, 219 and 81299, that added together give a palindrome (81518).

The spelling of 21981299 in words is "twenty-one million, nine hundred eighty-one thousand, two hundred ninety-nine".