21253157 has 4 divisors (see below), whose sum is σ = 21613440. Its totient is φ = 20892876.

The previous prime is 21253121. The next prime is 21253181. The reversal of 21253157 is 75135212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21253157 - 2⁶ = 21253093 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 (21253117) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 180053 + ... + 180170.

It is an arithmetic number, because the mean of its divisors is an integer number (5403360).

Almost surely, 2^21253157 is an apocalyptic number.

It is an amenable number.

21253157 is a deficient number, since it is larger than the sum of its proper divisors (360283).

21253157 is an equidigital number, since it uses as much as digits as its factorization.

21253157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360282.

The product of its digits is 2100, while the sum is 26.

The square root of 21253157 is about 4610.1146406570. The cubic root of 21253157 is about 276.9966287868.

Adding to 21253157 its reverse (75135212), we get a palindrome (96388369).

The spelling of 21253157 in words is "twenty-one million, two hundred fifty-three thousand, one hundred fifty-seven".