21211157 has 4 divisors (see below), whose sum is σ = 23139456. Its totient is φ = 19282860.

The previous prime is 21211139. The next prime is 21211181. The reversal of 21211157 is 75111212.

It is a happy number.

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 21211157 - 2⁸ = 21210901 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 (21201157) 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, 964133 + ... + 964154.

It is an arithmetic number, because the mean of its divisors is an integer number (5784864).

Almost surely, 2^21211157 is an apocalyptic number.

It is an amenable number.

21211157 is a deficient number, since it is larger than the sum of its proper divisors (1928299).

21211157 is a wasteful number, since it uses less digits than its factorization.

21211157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1928298.

The product of its digits is 140, while the sum is 20.

The square root of 21211157 is about 4605.5571867039. The cubic root of 21211157 is about 276.8140436717.

Adding to 21211157 its reverse (75111212), we get a palindrome (96322369).

The spelling of 21211157 in words is "twenty-one million, two hundred eleven thousand, one hundred fifty-seven".