21445851 has 32 divisors (see below), whose sum is σ = 35020800. Its totient is φ = 11400480.

The previous prime is 21445847. The next prime is 21445861. The reversal of 21445851 is 15854412.

It is not a de Polignac number, because 21445851 - 2² = 21445847 is a prime.

It is a super-2 number, since 2×21445851² = 919849050228402, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21445861) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 23086 + ... + 23996.

It is an arithmetic number, because the mean of its divisors is an integer number (1094400).

Almost surely, 2^21445851 is an apocalyptic number.

21445851 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21445851 is a deficient number, since it is larger than the sum of its proper divisors (13574949).

21445851 is a wasteful number, since it uses less digits than its factorization.

21445851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 999.

The product of its digits is 6400, while the sum is 30.

The square root of 21445851 is about 4630.9665297862. The cubic root of 21445851 is about 277.8312512107.

The spelling of 21445851 in words is "twenty-one million, four hundred forty-five thousand, eight hundred fifty-one".