21697871 has 8 divisors (see below), whose sum is σ = 23517984. Its totient is φ = 19899360.

The previous prime is 21697853. The next prime is 21697889. The reversal of 21697871 is 17879612.

It is an interprime number because it is at equal distance from previous prime (21697853) and next prime (21697889).

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

It is not a de Polignac number, because 21697871 - 2¹⁴ = 21681487 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 (21697801) 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 7 ways as a sum of consecutive naturals, for example, 3275 + ... + 7356.

It is an arithmetic number, because the mean of its divisors is an integer number (2939748).

Almost surely, 2^21697871 is an apocalyptic number.

21697871 is a deficient number, since it is larger than the sum of its proper divisors (1820113).

21697871 is a wasteful number, since it uses less digits than its factorization.

21697871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10801.

The product of its digits is 42336, while the sum is 41.

The square root of 21697871 is about 4658.0973583642. The cubic root of 21697871 is about 278.9153231124.

The spelling of 21697871 in words is "twenty-one million, six hundred ninety-seven thousand, eight hundred seventy-one".