21396919 has 4 divisors (see below), whose sum is σ = 21716344. Its totient is φ = 21077496.

The previous prime is 21396917. The next prime is 21396941. The reversal of 21396919 is 91969312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21396919 - 2¹ = 21396917 is a prime.

It is a super-2 number, since 2×21396919² = 915656285385122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21396917) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 159612 + ... + 159745.

It is an arithmetic number, because the mean of its divisors is an integer number (5429086).

Almost surely, 2^21396919 is an apocalyptic number.

21396919 is a deficient number, since it is larger than the sum of its proper divisors (319425).

21396919 is an equidigital number, since it uses as much as digits as its factorization.

21396919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319424.

The product of its digits is 26244, while the sum is 40.

The square root of 21396919 is about 4625.6803823870. The cubic root of 21396919 is about 277.6197854205.

It can be divided in two parts, 2139 and 6919, that multiplied together give a palindrome (14799741).

The spelling of 21396919 in words is "twenty-one million, three hundred ninety-six thousand, nine hundred nineteen".