20981642 has 24 divisors (see below), whose sum is σ = 34829508. Its totient is φ = 9472320.

The previous prime is 20981641. The next prime is 20981651. The reversal of 20981642 is 24618902.

It can be written as a sum of positive squares in 2 ways, for example, as 15594601 + 5387041 = 3949^2 + 2321^2 .

It is a junction number, because it is equal to n+sod(n) for n = 20981599 and 20981608.

It is not an unprimeable number, because it can be changed into a prime (20981641) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 66878 + ... + 67190.

Almost surely, 2^20981642 is an apocalyptic number.

20981642 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

20981642 is a deficient number, since it is larger than the sum of its proper divisors (13847866).

20981642 is a wasteful number, since it uses less digits than its factorization.

20981642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 614 (or 603 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 20981642 is about 4580.5722349942. The cubic root of 20981642 is about 275.8120000255.

The spelling of 20981642 in words is "twenty million, nine hundred eighty-one thousand, six hundred forty-two".