21239870 has 16 divisors (see below), whose sum is σ = 38348208. Its totient is φ = 8470080.

The previous prime is 21239839. The next prime is 21239899. The reversal of 21239870 is 7893212.

It is a super-2 number, since 2×21239870² = 902264155233800, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 410 + ... + 6530.

It is an arithmetic number, because the mean of its divisors is an integer number (2396763).

Almost surely, 2^21239870 is an apocalyptic number.

21239870 is a deficient number, since it is larger than the sum of its proper divisors (17108338).

21239870 is a wasteful number, since it uses less digits than its factorization.

21239870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6475.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 21239870 is about 4608.6733449009. The cubic root of 21239870 is about 276.9388927141.

The spelling of 21239870 in words is "twenty-one million, two hundred thirty-nine thousand, eight hundred seventy".