21872399 has 2 divisors, whose sum is σ = 21872400. Its totient is φ = 21872398.

The previous prime is 21872377. The next prime is 21872407. The reversal of 21872399 is 99327812.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21872399 - 2¹² = 21868303 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21872309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936199 + 10936200.

It is an arithmetic number, because the mean of its divisors is an integer number (10936200).

Almost surely, 2^21872399 is an apocalyptic number.

21872399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21872399 is an equidigital number, since it uses as much as digits as its factorization.

21872399 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 41.

The square root of 21872399 is about 4676.7936666054. The cubic root of 21872399 is about 279.6611504717.

The spelling of 21872399 in words is "twenty-one million, eight hundred seventy-two thousand, three hundred ninety-nine".