21287634 has 16 divisors (see below), whose sum is σ = 42641760. Its totient is φ = 7084800.

The previous prime is 21287633. The next prime is 21287641. The reversal of 21287634 is 43678212.

It is a super-3 number, since 3×21287634³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a junction number, because it is equal to n+sod(n) for n = 21287595 and 21287604.

It is not an unprimeable number, because it can be changed into a prime (21287633) 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, 2034 + ... + 6834.

It is an arithmetic number, because the mean of its divisors is an integer number (2665110).

Almost surely, 2^21287634 is an apocalyptic number.

21287634 is an abundant number, since it is smaller than the sum of its proper divisors (21354126).

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

21287634 is a wasteful number, since it uses less digits than its factorization.

21287634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5545.

The product of its digits is 16128, while the sum is 33.

The square root of 21287634 is about 4613.8524033610. The cubic root of 21287634 is about 277.1463297370.

The spelling of 21287634 in words is "twenty-one million, two hundred eighty-seven thousand, six hundred thirty-four".