21698501 has 4 divisors (see below), whose sum is σ = 23671104. Its totient is φ = 19725900.

The previous prime is 21698497. The next prime is 21698503. The reversal of 21698501 is 10589612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21698501 - 2² = 21698497 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21698503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 986285 + ... + 986306.

It is an arithmetic number, because the mean of its divisors is an integer number (5917776).

Almost surely, 2^21698501 is an apocalyptic number.

It is an amenable number.

21698501 is a deficient number, since it is larger than the sum of its proper divisors (1972603).

21698501 is a wasteful number, since it uses less digits than its factorization.

21698501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1972602.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21698501 is about 4658.1649820503. The cubic root of 21698501 is about 278.9180225316.

Subtracting from 21698501 its reverse (10589612), we obtain a square (11108889 = 3333²).

The spelling of 21698501 in words is "twenty-one million, six hundred ninety-eight thousand, five hundred one".