21424757 has 4 divisors (see below), whose sum is σ = 21439596. Its totient is φ = 21409920.

The previous prime is 21424699. The next prime is 21424759. The reversal of 21424757 is 75742412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12716356 + 8708401 = 3566^2 + 2951^2 .

It is a cyclic number.

It is not a de Polignac number, because 21424757 - 2⁶ = 21424693 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 (21424759) 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, 4988 + ... + 8229.

It is an arithmetic number, because the mean of its divisors is an integer number (5359899).

Almost surely, 2^21424757 is an apocalyptic number.

It is an amenable number.

21424757 is a deficient number, since it is larger than the sum of its proper divisors (14839).

21424757 is a wasteful number, since it uses less digits than its factorization.

21424757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14838.

The product of its digits is 15680, while the sum is 32.

The square root of 21424757 is about 4628.6884751515. The cubic root of 21424757 is about 277.7401303230.

The spelling of 21424757 in words is "twenty-one million, four hundred twenty-four thousand, seven hundred fifty-seven".