21399867 has 24 divisors (see below), whose sum is σ = 32757504. Its totient is φ = 13433904.

The previous prime is 21399839. The next prime is 21399901. The reversal of 21399867 is 76899312.

It is not a de Polignac number, because 21399867 - 2⁶ = 21399803 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21399167) 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, 13098 + ... + 14640.

It is an arithmetic number, because the mean of its divisors is an integer number (1364896).

Almost surely, 2^21399867 is an apocalyptic number.

21399867 is a deficient number, since it is larger than the sum of its proper divisors (11357637).

21399867 is a wasteful number, since it uses less digits than its factorization.

21399867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1639 (or 1636 counting only the distinct ones).

The product of its digits is 163296, while the sum is 45.

The square root of 21399867 is about 4625.9990272373. Note that the first 3 decimals coincide. The cubic root of 21399867 is about 277.6325346944.

The spelling of 21399867 in words is "twenty-one million, three hundred ninety-nine thousand, eight hundred sixty-seven".