21698821 has 8 divisors (see below), whose sum is σ = 22981824. Its totient is φ = 20444160.

The previous prime is 21698801. The next prime is 21698827. The reversal of 21698821 is 12889612.

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

It is a 5-Lehmer number, since φ(21698821) divides (21698821-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 21698821 - 2⁹ = 21698309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21698827) 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, 5500 + ... + 8581.

It is an arithmetic number, because the mean of its divisors is an integer number (2872728).

Almost surely, 2^21698821 is an apocalyptic number.

It is an amenable number.

21698821 is a deficient number, since it is larger than the sum of its proper divisors (1283003).

21698821 is a wasteful number, since it uses less digits than its factorization.

21698821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14171.

The product of its digits is 13824, while the sum is 37.

The square root of 21698821 is about 4658.1993302133. The cubic root of 21698821 is about 278.9193936452.

The spelling of 21698821 in words is "twenty-one million, six hundred ninety-eight thousand, eight hundred twenty-one".