21551157 has 8 divisors (see below), whose sum is σ = 31927680. Its totient is φ = 14367420.

The previous prime is 21551143. The next prime is 21551171. The reversal of 21551157 is 75115512.

It is an interprime number because it is at equal distance from previous prime (21551143) and next prime (21551171).

It is not a de Polignac number, because 21551157 - 2⁸ = 21550901 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 798191 = 21551157 / (2 + 1 + 5 + 5 + 1 + 1 + 5 + 7).

It is a self number, because there is not a number n which added to its sum of digits gives 21551157.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 399069 + ... + 399122.

It is an arithmetic number, because the mean of its divisors is an integer number (3990960).

Almost surely, 2^21551157 is an apocalyptic number.

21551157 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21551157 is a deficient number, since it is larger than the sum of its proper divisors (10376523).

21551157 is an equidigital number, since it uses as much as digits as its factorization.

21551157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 798200 (or 798194 counting only the distinct ones).

The product of its digits is 1750, while the sum is 27.

The square root of 21551157 is about 4642.3223713999. The cubic root of 21551157 is about 278.2852557386.

Adding to 21551157 its reverse (75115512), we get a palindrome (96666669).

The spelling of 21551157 in words is "twenty-one million, five hundred fifty-one thousand, one hundred fifty-seven".