21558157 has 2 divisors, whose sum is σ = 21558158. Its totient is φ = 21558156.

The previous prime is 21558151. The next prime is 21558181. The reversal of 21558157 is 75185512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20529961 + 1028196 = 4531^2 + 1014^2 .

It is a cyclic number.

It is not a de Polignac number, because 21558157 - 2³ = 21558149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21558151) 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 as a sum of consecutive naturals, namely, 10779078 + 10779079.

It is an arithmetic number, because the mean of its divisors is an integer number (10779079).

Almost surely, 2^21558157 is an apocalyptic number.

It is an amenable number.

21558157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21558157 is an equidigital number, since it uses as much as digits as its factorization.

21558157 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14000, while the sum is 34.

The square root of 21558157 is about 4643.0762431819. The cubic root of 21558157 is about 278.3153822870.

The spelling of 21558157 in words is "twenty-one million, five hundred fifty-eight thousand, one hundred fifty-seven".