21400919 has 2 divisors, whose sum is σ = 21400920. Its totient is φ = 21400918.

The previous prime is 21400913. The next prime is 21400921. The reversal of 21400919 is 91900412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21400919 - 2⁴ = 21400903 is a prime.

It is a super-2 number, since 2×21400919² = 915998668089122, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21400921, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21400913) 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, 10700459 + 10700460.

It is an arithmetic number, because the mean of its divisors is an integer number (10700460).

Almost surely, 2^21400919 is an apocalyptic number.

21400919 is a deficient number, since it is larger than the sum of its proper divisors (1).

21400919 is an equidigital number, since it uses as much as digits as its factorization.

21400919 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21400919 is about 4626.1127310086. The cubic root of 21400919 is about 277.6370840162.

The spelling of 21400919 in words is "twenty-one million, four hundred thousand, nine hundred nineteen".