21688154 has 8 divisors (see below), whose sum is σ = 32978100. Its totient is φ = 10695456.

The previous prime is 21688111. The next prime is 21688159. The reversal of 21688154 is 45188612.

It can be written as a sum of positive squares in 2 ways, for example, as 18705625 + 2982529 = 4325^2 + 1727^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21688159) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 74129 + ... + 74420.

Almost surely, 2^21688154 is an apocalyptic number.

21688154 is a deficient number, since it is larger than the sum of its proper divisors (11289946).

21688154 is a wasteful number, since it uses less digits than its factorization.

21688154 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148624.

The product of its digits is 15360, while the sum is 35.

The square root of 21688154 is about 4657.0542191390. The cubic root of 21688154 is about 278.8736811640.

The spelling of 21688154 in words is "twenty-one million, six hundred eighty-eight thousand, one hundred fifty-four".