21978974 has 8 divisors (see below), whose sum is σ = 33044880. Its totient is φ = 10964016.

The previous prime is 21978967. The next prime is 21978989. The reversal of 21978974 is 47987912.

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 (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11639 + ... + 13394.

It is an arithmetic number, because the mean of its divisors is an integer number (4130610).

Almost surely, 2^21978974 is an apocalyptic number.

21978974 is a deficient number, since it is larger than the sum of its proper divisors (11065906).

21978974 is a wasteful number, since it uses less digits than its factorization.

21978974 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25474.

The product of its digits is 254016, while the sum is 47.

The square root of 21978974 is about 4688.1738448995. The cubic root of 21978974 is about 280.1146384321.

The spelling of 21978974 in words is "twenty-one million, nine hundred seventy-eight thousand, nine hundred seventy-four".