21254157 has 20 divisors (see below), whose sum is σ = 31904796. Its totient is φ = 14100480.

The previous prime is 21254147. The next prime is 21254161. The reversal of 21254157 is 75145212.

It can be written as a sum of positive squares in 2 ways, for example, as 17816841 + 3437316 = 4221^2 + 1854^2 .

It is not a de Polignac number, because 21254157 - 2¹¹ = 21252109 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21254157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21254117) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 20307 + ... + 21327.

Almost surely, 2^21254157 is an apocalyptic number.

21254157 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21254157 is a deficient number, since it is larger than the sum of its proper divisors (10650639).

21254157 is a wasteful number, since it uses less digits than its factorization.

21254157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1290 (or 1281 counting only the distinct ones).

The product of its digits is 2800, while the sum is 27.

The square root of 21254157 is about 4610.2230965540. The cubic root of 21254157 is about 277.0009731184. Note that the first 3 decimals are identical.

Adding to 21254157 its reverse (75145212), we get a palindrome (96399369).

The spelling of 21254157 in words is "twenty-one million, two hundred fifty-four thousand, one hundred fifty-seven".