21978898 has 8 divisors (see below), whose sum is σ = 33365808. Its totient is φ = 10856964.

The previous prime is 21978893. The next prime is 21978899. The reversal of 21978898 is 89887912.

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 (21978893) 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, 66036 + ... + 66367.

It is an arithmetic number, because the mean of its divisors is an integer number (4170726).

Almost surely, 2^21978898 is an apocalyptic number.

21978898 is a deficient number, since it is larger than the sum of its proper divisors (11386910).

21978898 is a wasteful number, since it uses less digits than its factorization.

21978898 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132488.

The product of its digits is 580608, while the sum is 52.

The square root of 21978898 is about 4688.1657393910. The cubic root of 21978898 is about 280.1143155669.

The spelling of 21978898 in words is "twenty-one million, nine hundred seventy-eight thousand, eight hundred ninety-eight".