21998923 has 2 divisors, whose sum is σ = 21998924. Its totient is φ = 21998922.

The previous prime is 21998909. The next prime is 21998927. The reversal of 21998923 is 32989912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21998923 - 2⁹ = 21998411 is a prime.

It is a super-2 number, since 2×21998923² = 967905226319858, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21998923.

It is not a weakly prime, because it can be changed into another prime (21998927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10999461 + 10999462.

It is an arithmetic number, because the mean of its divisors is an integer number (10999462).

Almost surely, 2^21998923 is an apocalyptic number.

21998923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21998923 is an equidigital number, since it uses as much as digits as its factorization.

21998923 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 43.

The square root of 21998923 is about 4690.3009498325. The cubic root of 21998923 is about 280.1993605722.

The spelling of 21998923 in words is "twenty-one million, nine hundred ninety-eight thousand, nine hundred twenty-three".