21102157 has 4 divisors (see below), whose sum is σ = 21448156. Its totient is φ = 20756160.

The previous prime is 21102113. The next prime is 21102161. The reversal of 21102157 is 75120112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8185321 + 12916836 = 2861^2 + 3594^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21102157 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 (21102187) 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, 172908 + ... + 173029.

It is an arithmetic number, because the mean of its divisors is an integer number (5362039).

Almost surely, 2^21102157 is an apocalyptic number.

It is an amenable number.

21102157 is a deficient number, since it is larger than the sum of its proper divisors (345999).

21102157 is an equidigital number, since it uses as much as digits as its factorization.

21102157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345998.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 21102157 is about 4593.7084147778. The cubic root of 21102157 is about 276.3390646666.

Adding to 21102157 its reverse (75120112), we get a palindrome (96222269).

The spelling of 21102157 in words is "twenty-one million, one hundred two thousand, one hundred fifty-seven".