21747631 has 2 divisors, whose sum is σ = 21747632. Its totient is φ = 21747630.

The previous prime is 21747617. The next prime is 21747653. The reversal of 21747631 is 13674712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21747631 - 2¹⁵ = 21714863 is a prime.

It is a super-2 number, since 2×21747631² = 945918908224322, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21747593 and 21747602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21747431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10873815 + 10873816.

It is an arithmetic number, because the mean of its divisors is an integer number (10873816).

Almost surely, 2^21747631 is an apocalyptic number.

21747631 is a deficient number, since it is larger than the sum of its proper divisors (1).

21747631 is an equidigital number, since it uses as much as digits as its factorization.

21747631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7056, while the sum is 31.

The square root of 21747631 is about 4663.4355361686. The cubic root of 21747631 is about 279.1283736689.

The spelling of 21747631 in words is "twenty-one million, seven hundred forty-seven thousand, six hundred thirty-one".