21506838 has 16 divisors (see below), whose sum is σ = 43395696. Its totient is φ = 7105280.

The previous prime is 21506753. The next prime is 21506843. The reversal of 21506838 is 83860512.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21506799 and 21506808.

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, 15183 + ... + 16538.

It is an arithmetic number, because the mean of its divisors is an integer number (2712231).

Almost surely, 2^21506838 is an apocalyptic number.

21506838 is an abundant number, since it is smaller than the sum of its proper divisors (21888858).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21506838 is a wasteful number, since it uses less digits than its factorization.

21506838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31839.

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 21506838 is about 4637.5465496316. The cubic root of 21506838 is about 278.0943643906.

The spelling of 21506838 in words is "twenty-one million, five hundred six thousand, eight hundred thirty-eight".