21505160 has 32 divisors (see below), whose sum is σ = 49515840. Its totient is φ = 8401344.

The previous prime is 21505157. The next prime is 21505163. The reversal of 21505160 is 6150512.

It is an interprime number because it is at equal distance from previous prime (21505157) and next prime (21505163).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (21505163) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4532 + ... + 7971.

It is an arithmetic number, because the mean of its divisors is an integer number (1547370).

Almost surely, 2^21505160 is an apocalyptic number.

21505160 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21505160 is an abundant number, since it is smaller than the sum of its proper divisors (28010680).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21505160 is a wasteful number, since it uses less digits than its factorization.

21505160 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12557 (or 12553 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 21505160 is about 4637.3656314766. The cubic root of 21505160 is about 278.0871317377.

Adding to 21505160 its reverse (6150512), we get a palindrome (27655672).

The spelling of 21505160 in words is "twenty-one million, five hundred five thousand, one hundred sixty".