20998781 has 8 divisors (see below), whose sum is σ = 22170720. Its totient is φ = 19833552.

The previous prime is 20998777. The next prime is 20998787. The reversal of 20998781 is 18789902.

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

It is a cyclic number.

It is not a de Polignac number, because 20998781 - 2² = 20998777 is a prime.

It is a super-2 number, since 2×20998781² = 881897606971922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20998787) 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, 5606 + ... + 8568.

It is an arithmetic number, because the mean of its divisors is an integer number (2771340).

Almost surely, 2^20998781 is an apocalyptic number.

It is an amenable number.

20998781 is a deficient number, since it is larger than the sum of its proper divisors (1171939).

20998781 is a wasteful number, since it uses less digits than its factorization.

20998781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3355.

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 20998781 is about 4582.4426892215. The cubic root of 20998781 is about 275.8870792355.

The spelling of 20998781 in words is "twenty million, nine hundred ninety-eight thousand, seven hundred eighty-one".