20921998 has 8 divisors (see below), whose sum is σ = 31410720. Its totient is φ = 10451760.

The previous prime is 20921987. The next prime is 20922017. The reversal of 20921998 is 89912902.

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

It is a self number, because there is not a number n which added to its sum of digits gives 20921998.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1318 + ... + 6601.

It is an arithmetic number, because the mean of its divisors is an integer number (3926340).

Almost surely, 2^20921998 is an apocalyptic number.

20921998 is a deficient number, since it is larger than the sum of its proper divisors (10488722).

20921998 is a wasteful number, since it uses less digits than its factorization.

20921998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9242.

The product of its (nonzero) digits is 23328, while the sum is 40.

The square root of 20921998 is about 4574.0570612969. The cubic root of 20921998 is about 275.5504039846.

The spelling of 20921998 in words is "twenty million, nine hundred twenty-one thousand, nine hundred ninety-eight".