21684971 has 8 divisors (see below), whose sum is σ = 27035904. Its totient is φ = 16897320.

The previous prime is 21684967. The next prime is 21684977. The reversal of 21684971 is 17948612.

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

It is not a de Polignac number, because 21684971 - 2² = 21684967 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21684977) 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, 140735 + ... + 140888.

It is an arithmetic number, because the mean of its divisors is an integer number (3379488).

Almost surely, 2^21684971 is an apocalyptic number.

21684971 is a deficient number, since it is larger than the sum of its proper divisors (5350933).

21684971 is a wasteful number, since it uses less digits than its factorization.

21684971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281641.

The product of its digits is 24192, while the sum is 38.

The square root of 21684971 is about 4656.7124669664. The cubic root of 21684971 is about 278.8600377967.

The spelling of 21684971 in words is "twenty-one million, six hundred eighty-four thousand, nine hundred seventy-one".