20400981 has 8 divisors (see below), whose sum is σ = 27227424. Its totient is φ = 13587600.

The previous prime is 20400967. The next prime is 20400997. The reversal of 20400981 is 18900402.

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

It is not a de Polignac number, because 20400981 - 2⁹ = 20400469 is a prime.

It is a super-3 number, since 3×20400981³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20400481) 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, 1290 + ... + 6516.

It is an arithmetic number, because the mean of its divisors is an integer number (3403428).

Almost surely, 2^20400981 is an apocalyptic number.

It is an amenable number.

20400981 is a deficient number, since it is larger than the sum of its proper divisors (6826443).

20400981 is a wasteful number, since it uses less digits than its factorization.

20400981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6531.

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 20400981 is about 4516.7445134743. The cubic root of 20400981 is about 273.2438214068.

The spelling of 20400981 in words is "twenty million, four hundred thousand, nine hundred eighty-one".