20978945 has 16 divisors (see below), whose sum is σ = 28539840. Its totient is φ = 14675904.

The previous prime is 20978941. The next prime is 20978981. The reversal of 20978945 is 54987902.

It is a happy number.

It is not a de Polignac number, because 20978945 - 2² = 20978941 is a prime.

It is a super-2 number, since 2×20978945² = 880232266626050, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20978896 and 20978905.

It is not an unprimeable number, because it can be changed into a prime (20978941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7259 + ... + 9728.

It is an arithmetic number, because the mean of its divisors is an integer number (1783740).

Almost surely, 2^20978945 is an apocalyptic number.

It is an amenable number.

20978945 is a deficient number, since it is larger than the sum of its proper divisors (7560895).

20978945 is a wasteful number, since it uses less digits than its factorization.

20978945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17024.

The product of its (nonzero) digits is 181440, while the sum is 44.

The square root of 20978945 is about 4580.2778300011. The cubic root of 20978945 is about 275.8001818078.

The spelling of 20978945 in words is "twenty million, nine hundred seventy-eight thousand, nine hundred forty-five".