21698257 has 8 divisors (see below), whose sum is σ = 24872256. Its totient is φ = 18542832.

The previous prime is 21698213. The next prime is 21698267. The reversal of 21698257 is 75289612.

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

It is not a de Polignac number, because 21698257 - 2¹⁵ = 21665489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21698207) 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, 2038 + ... + 6895.

It is an arithmetic number, because the mean of its divisors is an integer number (3109032).

Almost surely, 2^21698257 is an apocalyptic number.

It is an amenable number.

21698257 is a deficient number, since it is larger than the sum of its proper divisors (3173999).

21698257 is an equidigital number, since it uses as much as digits as its factorization.

21698257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9287.

The product of its digits is 60480, while the sum is 40.

The square root of 21698257 is about 4658.1387914059. The cubic root of 21698257 is about 278.9169770485.

The spelling of 21698257 in words is "twenty-one million, six hundred ninety-eight thousand, two hundred fifty-seven".