21405868 has 36 divisors (see below), whose sum is σ = 42096096. Its totient is φ = 9512800.

The previous prime is 21405829. The next prime is 21405871. The reversal of 21405868 is 86850412.

It is a super-2 number, since 2×21405868² = 916422369666848, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22278 + ... + 23218.

It is an arithmetic number, because the mean of its divisors is an integer number (1169336).

Almost surely, 2^21405868 is an apocalyptic number.

It is an amenable number.

21405868 is a deficient number, since it is larger than the sum of its proper divisors (20690228).

21405868 is a wasteful number, since it uses less digits than its factorization.

21405868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1014 (or 1001 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 34.

The square root of 21405868 is about 4626.6475984237. The cubic root of 21405868 is about 277.6584837207.

It can be divided in two parts, 2140 and 5868, that added together give a palindrome (8008).

The spelling of 21405868 in words is "twenty-one million, four hundred five thousand, eight hundred sixty-eight".