21757397 has 8 divisors (see below), whose sum is σ = 22035552. Its totient is φ = 21481200.

The previous prime is 21757387. The next prime is 21757409. The reversal of 21757397 is 79375712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21757397 - 2¹⁰ = 21756373 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 (21757327) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39947 + ... + 40487.

It is an arithmetic number, because the mean of its divisors is an integer number (2754444).

Almost surely, 2^21757397 is an apocalyptic number.

It is an amenable number.

21757397 is a deficient number, since it is larger than the sum of its proper divisors (278155).

21757397 is a wasteful number, since it uses less digits than its factorization.

21757397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 979.

The product of its digits is 92610, while the sum is 41.

The square root of 21757397 is about 4664.4825007711. The cubic root of 21757397 is about 279.1701492499.

The spelling of 21757397 in words is "twenty-one million, seven hundred fifty-seven thousand, three hundred ninety-seven".