21521743 has 2 divisors, whose sum is σ = 21521744. Its totient is φ = 21521742.

The previous prime is 21521701. The next prime is 21521771. The reversal of 21521743 is 34712512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21521743 - 2¹⁷ = 21390671 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21528743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760871 + 10760872.

It is an arithmetic number, because the mean of its divisors is an integer number (10760872).

Almost surely, 2^21521743 is an apocalyptic number.

21521743 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521743 is an equidigital number, since it uses as much as digits as its factorization.

21521743 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 25.

The square root of 21521743 is about 4639.1532632583. The cubic root of 21521743 is about 278.1585926348.

The spelling of 21521743 in words is "twenty-one million, five hundred twenty-one thousand, seven hundred forty-three".