20978961 has 8 divisors (see below), whose sum is σ = 27996960. Its totient is φ = 13973472.

The previous prime is 20978941. The next prime is 20978981. The reversal of 20978961 is 16987902.

It is an interprime number because it is at equal distance from previous prime (20978941) and next prime (20978981).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20978961 - 2⁶ = 20978897 is a prime.

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

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1981 + ... + 6773.

It is an arithmetic number, because the mean of its divisors is an integer number (3499620).

Almost surely, 2^20978961 is an apocalyptic number.

It is an amenable number.

20978961 is a deficient number, since it is larger than the sum of its proper divisors (7017999).

20978961 is a wasteful number, since it uses less digits than its factorization.

20978961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6255.

The product of its (nonzero) digits is 54432, while the sum is 42.

The square root of 20978961 is about 4580.2795766198. The cubic root of 20978961 is about 275.8002519225.

Adding to 20978961 its sum of digits (42), we get a triangular number (20979003 = T₆₄₇₇).

The spelling of 20978961 in words is "twenty million, nine hundred seventy-eight thousand, nine hundred sixty-one".