21918457 has 32 divisors (see below), whose sum is σ = 27648000. Its totient is φ = 17107200.

The previous prime is 21918443. The next prime is 21918473. The reversal of 21918457 is 75481912.

It is not a de Polignac number, because 21918457 - 2⁷ = 21918329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21918427) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 110044 + ... + 110242.

It is an arithmetic number, because the mean of its divisors is an integer number (864000).

Almost surely, 2^21918457 is an apocalyptic number.

It is an amenable number.

21918457 is a deficient number, since it is larger than the sum of its proper divisors (5729543).

21918457 is a wasteful number, since it uses less digits than its factorization.

21918457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 277.

The product of its digits is 20160, while the sum is 37.

The square root of 21918457 is about 4681.7151771546. The cubic root of 21918457 is about 279.8573125031.

It can be divided in two parts, 2191 and 8457, that added together give a cube (10648 = 22³).

The spelling of 21918457 in words is "twenty-one million, nine hundred eighteen thousand, four hundred fifty-seven".