21157678 has 8 divisors (see below), whose sum is σ = 33406920. Its totient is φ = 10022040.

The previous prime is 21157649. The next prime is 21157693. The reversal of 21157678 is 87675112.

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

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 278353 + ... + 278428.

It is an arithmetic number, because the mean of its divisors is an integer number (4175865).

Almost surely, 2^21157678 is an apocalyptic number.

21157678 is a deficient number, since it is larger than the sum of its proper divisors (12249242).

21157678 is a wasteful number, since it uses less digits than its factorization.

21157678 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556802.

The product of its digits is 23520, while the sum is 37.

The square root of 21157678 is about 4599.7476017712. The cubic root of 21157678 is about 276.5812071336.

The spelling of 21157678 in words is "twenty-one million, one hundred fifty-seven thousand, six hundred seventy-eight".