21601287 has 6 divisors (see below), whose sum is σ = 31201872. Its totient is φ = 14400852.

The previous prime is 21601277. The next prime is 21601319. The reversal of 21601287 is 78210612.

It is not a de Polignac number, because 21601287 - 2¹⁰ = 21600263 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21601287.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21601277) 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 5 ways as a sum of consecutive naturals, for example, 1200063 + ... + 1200080.

It is an arithmetic number, because the mean of its divisors is an integer number (5200312).

Almost surely, 2^21601287 is an apocalyptic number.

21601287 is a deficient number, since it is larger than the sum of its proper divisors (9600585).

21601287 is a wasteful number, since it uses less digits than its factorization.

21601287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2400149 (or 2400146 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21601287 is about 4647.7184725411. The cubic root of 21601287 is about 278.5008611336.

Adding to 21601287 its reverse (78210612), we get a palindrome (99811899).

The spelling of 21601287 in words is "twenty-one million, six hundred one thousand, two hundred eighty-seven".