21123719 has 4 divisors (see below), whose sum is σ = 21231144. Its totient is φ = 21016296.

The previous prime is 21123709. The next prime is 21123721. The reversal of 21123719 is 91732112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123719 is a prime.

It is a super-2 number, since 2×21123719² = 892423008781922, 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 (21123709) 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, 53417 + ... + 53810.

It is an arithmetic number, because the mean of its divisors is an integer number (5307786).

Almost surely, 2^21123719 is an apocalyptic number.

21123719 is a deficient number, since it is larger than the sum of its proper divisors (107425).

21123719 is a wasteful number, since it uses less digits than its factorization.

21123719 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107424.

The product of its digits is 756, while the sum is 26.

The square root of 21123719 is about 4596.0547211712. The cubic root of 21123719 is about 276.4331529098.

The spelling of 21123719 in words is "twenty-one million, one hundred twenty-three thousand, seven hundred nineteen".