20847981 has 24 divisors (see below), whose sum is σ = 35277984. Its totient is φ = 10829280.

The previous prime is 20847979. The next prime is 20848007. The reversal of 20847981 is 18974802.

It is not a de Polignac number, because 20847981 - 2¹ = 20847979 is a prime.

It is a super-2 number, since 2×20847981² = 869276623552722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20847941) 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, 4830 + ... + 8063.

It is an arithmetic number, because the mean of its divisors is an integer number (1469916).

Almost surely, 2^20847981 is an apocalyptic number.

20847981 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20847981 is a deficient number, since it is larger than the sum of its proper divisors (14430003).

20847981 is a wasteful number, since it uses less digits than its factorization.

20847981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12921 (or 12914 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 20847981 is about 4565.9589354264. The cubic root of 20847981 is about 275.2250763400.

The spelling of 20847981 in words is "twenty million, eight hundred forty-seven thousand, nine hundred eighty-one".