21079978 has 8 divisors (see below), whose sum is σ = 31642272. Its totient is φ = 10532556.

The previous prime is 21079931. The next prime is 21079979. The reversal of 21079978 is 87997012.

It is a happy number.

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 (21079979) 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, 1051 + ... + 6577.

It is an arithmetic number, because the mean of its divisors is an integer number (3955284).

Almost surely, 2^21079978 is an apocalyptic number.

21079978 is a deficient number, since it is larger than the sum of its proper divisors (10562294).

21079978 is a wasteful number, since it uses less digits than its factorization.

21079978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7436.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 21079978 is about 4591.2937174613. The cubic root of 21079978 is about 276.2422171801.

The spelling of 21079978 in words is "twenty-one million, seventy-nine thousand, nine hundred seventy-eight".