20847978 has 48 divisors (see below), whose sum is σ = 48597120. Its totient is φ = 6438528.

The previous prime is 20847977. The next prime is 20847979. The reversal of 20847978 is 87974802.

It is an interprime number because it is at equal distance from previous prime (20847977) and next prime (20847979).

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (20847971) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15426 + ... + 16722.

It is an arithmetic number, because the mean of its divisors is an integer number (1012440).

Almost surely, 2^20847978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20847978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24298560).

20847978 is an abundant number, since it is smaller than the sum of its proper divisors (27749142).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20847978 is a wasteful number, since it uses less digits than its factorization.

20847978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1371 (or 1368 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 45.

The square root of 20847978 is about 4565.9586069083. The cubic root of 20847978 is about 275.2250631384.

The spelling of 20847978 in words is "twenty million, eight hundred forty-seven thousand, nine hundred seventy-eight".