21308157 has 32 divisors (see below), whose sum is σ = 36005760. Its totient is φ = 12337920.

The previous prime is 21308153. The next prime is 21308167. The reversal of 21308157 is 75180312.

It is not a de Polignac number, because 21308157 - 2² = 21308153 is a prime.

It is a super-4 number, since 4×21308157⁴ (a number of 30 digits) contains 4444 as substring.

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 21308157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308153) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4182 + ... + 7752.

It is an arithmetic number, because the mean of its divisors is an integer number (1125180).

Almost surely, 2^21308157 is an apocalyptic number.

21308157 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21308157 is a deficient number, since it is larger than the sum of its proper divisors (14697603).

21308157 is a wasteful number, since it uses less digits than its factorization.

21308157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3610 (or 3604 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 21308157 is about 4616.0759309179. The cubic root of 21308157 is about 277.2353649526.

Adding to 21308157 its reverse (75180312), we get a palindrome (96488469).

The spelling of 21308157 in words is "twenty-one million, three hundred eight thousand, one hundred fifty-seven".