21955919 has 2 divisors, whose sum is σ = 21955920. Its totient is φ = 21955918.

The previous prime is 21955889. The next prime is 21955931. The reversal of 21955919 is 91955912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21955919 - 2¹⁶ = 21890383 is a prime.

It is a super-2 number, since 2×21955919² = 964124758269122, which contains 22 as substring.

It is a Sophie Germain 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 (21255919) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10977959 + 10977960.

It is an arithmetic number, because the mean of its divisors is an integer number (10977960).

Almost surely, 2^21955919 is an apocalyptic number.

21955919 is a deficient number, since it is larger than the sum of its proper divisors (1).

21955919 is an equidigital number, since it uses as much as digits as its factorization.

21955919 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36450, while the sum is 41.

The square root of 21955919 is about 4685.7143532230. The cubic root of 21955919 is about 280.0166614235.

The spelling of 21955919 in words is "twenty-one million, nine hundred fifty-five thousand, nine hundred nineteen".