21641951 has 4 divisors (see below), whose sum is σ = 21653400. Its totient is φ = 21630504.

The previous prime is 21641947. The next prime is 21641957. The reversal of 21641951 is 15914612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21641951 - 2² = 21641947 is a prime.

It is a super-3 number, since 3×21641951³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641957) 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, 2141 + ... + 6918.

It is an arithmetic number, because the mean of its divisors is an integer number (5413350).

Almost surely, 2^21641951 is an apocalyptic number.

21641951 is a deficient number, since it is larger than the sum of its proper divisors (11449).

21641951 is an equidigital number, since it uses as much as digits as its factorization.

21641951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11448.

The product of its digits is 2160, while the sum is 29.

The square root of 21641951 is about 4652.0910352228. The cubic root of 21641951 is about 278.6755090624.

The spelling of 21641951 in words is "twenty-one million, six hundred forty-one thousand, nine hundred fifty-one".