20211978 has 16 divisors (see below), whose sum is σ = 41364576. Its totient is φ = 6580560.

The previous prime is 20211977. The next prime is 20212001. The reversal of 20211978 is 87911202.

It is not an unprimeable number, because it can be changed into a prime (20211973) 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, 38913 + ... + 39428.

It is an arithmetic number, because the mean of its divisors is an integer number (2585286).

Almost surely, 2^20211978 is an apocalyptic number.

20211978 is an abundant number, since it is smaller than the sum of its proper divisors (21152598).

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

20211978 is a wasteful number, since it uses less digits than its factorization.

20211978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78389.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 20211978 is about 4495.7733483796. The cubic root of 20211978 is about 272.3973880693.

The spelling of 20211978 in words is "twenty million, two hundred eleven thousand, nine hundred seventy-eight".