21980999 has 2 divisors, whose sum is σ = 21981000. Its totient is φ = 21980998.

The previous prime is 21980993. The next prime is 21981013. The reversal of 21980999 is 99908912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21980999 - 2¹⁶ = 21915463 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21980993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990499 + 10990500.

It is an arithmetic number, because the mean of its divisors is an integer number (10990500).

Almost surely, 2^21980999 is an apocalyptic number.

21980999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21980999 is an equidigital number, since it uses as much as digits as its factorization.

21980999 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 104976, while the sum is 47.

The square root of 21980999 is about 4688.3898088790. The cubic root of 21980999 is about 280.1232408161.

It can be divided in two parts, 219 and 80999, that added together give a palindrome (81218).

The spelling of 21980999 in words is "twenty-one million, nine hundred eighty thousand, nine hundred ninety-nine".