21512747 has 2 divisors, whose sum is σ = 21512748. Its totient is φ = 21512746.

The previous prime is 21512719. The next prime is 21512749. The reversal of 21512747 is 74721512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21512747 - 2¹⁰ = 21511723 is a prime.

Together with 21512749, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21512749) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756373 + 10756374.

It is an arithmetic number, because the mean of its divisors is an integer number (10756374).

Almost surely, 2^21512747 is an apocalyptic number.

21512747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21512747 is an equidigital number, since it uses as much as digits as its factorization.

21512747 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3920, while the sum is 29.

The square root of 21512747 is about 4638.1835884320. The cubic root of 21512747 is about 278.1198308512.

The spelling of 21512747 in words is "twenty-one million, five hundred twelve thousand, seven hundred forty-seven".