21907842 has 16 divisors (see below), whose sum is σ = 47799072. Its totient is φ = 6638720.

The previous prime is 21907841. The next prime is 21907867. The reversal of 21907842 is 24870912.

It is a happy number.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21907841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 165903 + ... + 166034.

It is an arithmetic number, because the mean of its divisors is an integer number (2987442).

Almost surely, 2^21907842 is an apocalyptic number.

21907842 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21907842 is an abundant number, since it is smaller than the sum of its proper divisors (25891230).

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

21907842 is a wasteful number, since it uses less digits than its factorization.

21907842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 331953.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21907842 is about 4680.5813741457. The cubic root of 21907842 is about 279.8121273720.

The spelling of 21907842 in words is "twenty-one million, nine hundred seven thousand, eight hundred forty-two".