21423791 has 4 divisors (see below), whose sum is σ = 22684032. Its totient is φ = 20163552.

The previous prime is 21423781. The next prime is 21423793. The reversal of 21423791 is 19732412.

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-21423791 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423793) 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, 630095 + ... + 630128.

It is an arithmetic number, because the mean of its divisors is an integer number (5671008).

Almost surely, 2^21423791 is an apocalyptic number.

21423791 is a deficient number, since it is larger than the sum of its proper divisors (1260241).

21423791 is a wasteful number, since it uses less digits than its factorization.

21423791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1260240.

The product of its digits is 3024, while the sum is 29.

The square root of 21423791 is about 4628.5841247621. The cubic root of 21423791 is about 277.7359560089.

The spelling of 21423791 in words is "twenty-one million, four hundred twenty-three thousand, seven hundred ninety-one".