21731519 has 2 divisors, whose sum is σ = 21731520. Its totient is φ = 21731518.

The previous prime is 21731509. The next prime is 21731533. The reversal of 21731519 is 91513712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21731519 - 2⁸ = 21731263 is a prime.

It is a super-2 number, since 2×21731519² = 944517836094722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21731491 and 21731500.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21731509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865759 + 10865760.

It is an arithmetic number, because the mean of its divisors is an integer number (10865760).

Almost surely, 2^21731519 is an apocalyptic number.

21731519 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731519 is an equidigital number, since it uses as much as digits as its factorization.

21731519 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1890, while the sum is 29.

The square root of 21731519 is about 4661.7077342965. The cubic root of 21731519 is about 279.0594247423.

The spelling of 21731519 in words is "twenty-one million, seven hundred thirty-one thousand, five hundred nineteen".