21397719 has 16 divisors (see below), whose sum is σ = 33658880. Its totient is φ = 11832480.

The previous prime is 21397711. The next prime is 21397769. The reversal of 21397719 is 91779312.

It is not a de Polignac number, because 21397719 - 2³ = 21397711 is a prime.

It is a super-2 number, since 2×21397719² = 915724756805922, 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 (21397711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15784 + ... + 17085.

It is an arithmetic number, because the mean of its divisors is an integer number (2103680).

Almost surely, 2^21397719 is an apocalyptic number.

21397719 is a deficient number, since it is larger than the sum of its proper divisors (12261161).

21397719 is a wasteful number, since it uses less digits than its factorization.

21397719 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32910.

The product of its digits is 23814, while the sum is 39.

The square root of 21397719 is about 4625.7668553441. The cubic root of 21397719 is about 277.6232453121.

The spelling of 21397719 in words is "twenty-one million, three hundred ninety-seven thousand, seven hundred nineteen".