21228157 has 6 divisors (see below), whose sum is σ = 21408734. Its totient is φ = 21049080.

The previous prime is 21228139. The next prime is 21228167. The reversal of 21228157 is 75182212.

It can be written as a sum of positive squares in only one way, i.e., 19838116 + 1390041 = 4454^2 + 1179^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21228157 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 (21228167) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 16543 + ... + 17779.

Almost surely, 2^21228157 is an apocalyptic number.

It is an amenable number.

21228157 is a deficient number, since it is larger than the sum of its proper divisors (180577).

21228157 is an equidigital number, since it uses as much as digits as its factorization.

21228157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1499 (or 1368 counting only the distinct ones).

The product of its digits is 2240, while the sum is 28.

The square root of 21228157 is about 4607.4024135081. The cubic root of 21228157 is about 276.8879761798.

The spelling of 21228157 in words is "twenty-one million, two hundred twenty-eight thousand, one hundred fifty-seven".