21939451 has 4 divisors (see below), whose sum is σ = 21987504. Its totient is φ = 21891400.

The previous prime is 21939439. The next prime is 21939461. The reversal of 21939451 is 15493912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21939451 - 2⁵ = 21939419 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21939461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23335 + ... + 24256.

It is an arithmetic number, because the mean of its divisors is an integer number (5496876).

Almost surely, 2^21939451 is an apocalyptic number.

21939451 is a deficient number, since it is larger than the sum of its proper divisors (48053).

21939451 is an equidigital number, since it uses as much as digits as its factorization.

21939451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48052.

The product of its digits is 9720, while the sum is 34.

The square root of 21939451 is about 4683.9567675204. The cubic root of 21939451 is about 279.9466352381.

The spelling of 21939451 in words is "twenty-one million, nine hundred thirty-nine thousand, four hundred fifty-one".