21680019 has 24 divisors (see below), whose sum is σ = 32348160. Its totient is φ = 13984368.

The previous prime is 21680017. The next prime is 21680027. The reversal of 21680019 is 91008612.

It is not a de Polignac number, because 21680019 - 2¹ = 21680017 is a prime.

It is a super-2 number, since 2×21680019² = 940046447680722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21679974 and 21680001.

It is not an unprimeable number, because it can be changed into a prime (21680017) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 45022 + ... + 45500.

It is an arithmetic number, because the mean of its divisors is an integer number (1347840).

Almost surely, 2^21680019 is an apocalyptic number.

21680019 is a deficient number, since it is larger than the sum of its proper divisors (10668141).

21680019 is a wasteful number, since it uses less digits than its factorization.

21680019 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 639 (or 636 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 21680019 is about 4656.1807310284. The cubic root of 21680019 is about 278.8388092688.

The spelling of 21680019 in words is "twenty-one million, six hundred eighty thousand, nineteen".