20421157 has 8 divisors (see below), whose sum is σ = 21595392. Its totient is φ = 19279200.

The previous prime is 20421103. The next prime is 20421179. The reversal of 20421157 is 75112402.

It is a happy number.

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 20421157 - 2¹⁹ = 19896869 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 (20421187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6763 + ... + 9304.

It is an arithmetic number, because the mean of its divisors is an integer number (2699424).

Almost surely, 2^20421157 is an apocalyptic number.

It is an amenable number.

20421157 is a deficient number, since it is larger than the sum of its proper divisors (1174235).

20421157 is a wasteful number, since it uses less digits than its factorization.

20421157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16139.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 20421157 is about 4518.9774285783. The cubic root of 20421157 is about 273.3338685626. Note that the first 3 decimals are identical.

Adding to 20421157 its reverse (75112402), we get a palindrome (95533559).

The spelling of 20421157 in words is "twenty million, four hundred twenty-one thousand, one hundred fifty-seven".