20961918 has 48 divisors (see below), whose sum is σ = 48920976. Its totient is φ = 6462720.

The previous prime is 20961911. The next prime is 20961929. The reversal of 20961918 is 81916902.

20961918 is a `hidden beast` number, since 20 + 9 + 619 + 18 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20961911) 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, 18105 + ... + 19227.

It is an arithmetic number, because the mean of its divisors is an integer number (1019187).

Almost surely, 2^20961918 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20961918, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24460488).

20961918 is an abundant number, since it is smaller than the sum of its proper divisors (27959058).

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

20961918 is a wasteful number, since it uses less digits than its factorization.

20961918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1209 (or 1206 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 20961918 is about 4578.4187226596. The cubic root of 20961918 is about 275.7255463301.

The spelling of 20961918 in words is "twenty million, nine hundred sixty-one thousand, nine hundred eighteen".