21939858 has 48 divisors (see below), whose sum is σ = 49177440. Its totient is φ = 7065792.

The previous prime is 21939839. The next prime is 21939859. The reversal of 21939858 is 85893912.

It is a happy number.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21939859) 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, 77385 + ... + 77667.

It is an arithmetic number, because the mean of its divisors is an integer number (1024530).

Almost surely, 2^21939858 is an apocalyptic number.

21939858 is an abundant number, since it is smaller than the sum of its proper divisors (27237582).

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

21939858 is a wasteful number, since it uses less digits than its factorization.

21939858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 423 (or 420 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 21939858 is about 4684.0002134927. Note that the first 3 decimals coincide. The cubic root of 21939858 is about 279.9483663294.

The spelling of 21939858 in words is "twenty-one million, nine hundred thirty-nine thousand, eight hundred fifty-eight".