21438291 has 16 divisors (see below), whose sum is σ = 32868864. Its totient is φ = 12175104.

The previous prime is 21438283. The next prime is 21438301. The reversal of 21438291 is 19283412.

It is not a de Polignac number, because 21438291 - 2³ = 21438283 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21438211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 451 + ... + 6563.

It is an arithmetic number, because the mean of its divisors is an integer number (2054304).

Almost surely, 2^21438291 is an apocalyptic number.

21438291 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21438291 is a deficient number, since it is larger than the sum of its proper divisors (11430573).

21438291 is a wasteful number, since it uses less digits than its factorization.

21438291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6290.

The product of its digits is 3456, while the sum is 30.

The square root of 21438291 is about 4630.1502135460. The cubic root of 21438291 is about 277.7986007442.

The spelling of 21438291 in words is "twenty-one million, four hundred thirty-eight thousand, two hundred ninety-one".