21225157 has 4 divisors (see below), whose sum is σ = 21284640. Its totient is φ = 21165676.

The previous prime is 21225121. The next prime is 21225179. The reversal of 21225157 is 75152212.

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 a de Polignac number, because none of the positive numbers 2^k-21225157 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 (21226157) 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, 29203 + ... + 29920.

It is an arithmetic number, because the mean of its divisors is an integer number (5321160).

Almost surely, 2^21225157 is an apocalyptic number.

It is an amenable number.

21225157 is a deficient number, since it is larger than the sum of its proper divisors (59483).

21225157 is an equidigital number, since it uses as much as digits as its factorization.

21225157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59482.

The product of its digits is 1400, while the sum is 25.

The square root of 21225157 is about 4607.0768389511. The cubic root of 21225157 is about 276.8749321355.

Adding to 21225157 its reverse (75152212), we get a palindrome (96377369).

The spelling of 21225157 in words is "twenty-one million, two hundred twenty-five thousand, one hundred fifty-seven".