21541631 has 2 divisors, whose sum is σ = 21541632. Its totient is φ = 21541630.

The previous prime is 21541607. The next prime is 21541633. The reversal of 21541631 is 13614512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21541631 is a prime.

It is a super-2 number, since 2×21541631² = 928083732280322, which contains 22 as substring.

Together with 21541633, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21541597 and 21541606.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21541633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770815 + 10770816.

It is an arithmetic number, because the mean of its divisors is an integer number (10770816).

Almost surely, 2^21541631 is an apocalyptic number.

21541631 is a deficient number, since it is larger than the sum of its proper divisors (1).

21541631 is an equidigital number, since it uses as much as digits as its factorization.

21541631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 23.

The square root of 21541631 is about 4641.2962628990. The cubic root of 21541631 is about 278.2442473289.

The spelling of 21541631 in words is "twenty-one million, five hundred forty-one thousand, six hundred thirty-one".