21984157 has 8 divisors (see below), whose sum is σ = 23942520. Its totient is φ = 20064000.

The previous prime is 21984143. The next prime is 21984161. The reversal of 21984157 is 75148912.

It can be written as a sum of positive squares in 4 ways, for example, as 556516 + 21427641 = 746^2 + 4629^2 .

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 21984157 - 2¹⁵ = 21951389 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 (21984187) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8344 + ... + 10657.

It is an arithmetic number, because the mean of its divisors is an integer number (2992815).

Almost surely, 2^21984157 is an apocalyptic number.

It is an amenable number.

21984157 is a deficient number, since it is larger than the sum of its proper divisors (1958363).

21984157 is a wasteful number, since it uses less digits than its factorization.

21984157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19103.

The product of its digits is 20160, while the sum is 37.

The square root of 21984157 is about 4688.7265861852. The cubic root of 21984157 is about 280.1366552327.

The spelling of 21984157 in words is "twenty-one million, nine hundred eighty-four thousand, one hundred fifty-seven".