21915418 has 16 divisors (see below), whose sum is σ = 37721664. Its totient is φ = 9354240.

The previous prime is 21915407. The next prime is 21915427. The reversal of 21915418 is 81451912.

It is a happy number.

It is a super-2 number, since 2×21915418² = 960571092229448, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21915418.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 553 + ... + 6643.

It is an arithmetic number, because the mean of its divisors is an integer number (2357604).

Almost surely, 2^21915418 is an apocalyptic number.

21915418 is a deficient number, since it is larger than the sum of its proper divisors (15806246).

21915418 is a wasteful number, since it uses less digits than its factorization.

21915418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6357.

The product of its digits is 2880, while the sum is 31.

The square root of 21915418 is about 4681.3906053650. The cubic root of 21915418 is about 279.8443778079.

The spelling of 21915418 in words is "twenty-one million, nine hundred fifteen thousand, four hundred eighteen".