21534991 has 2 divisors, whose sum is σ = 21534992. Its totient is φ = 21534990.

The previous prime is 21534983. The next prime is 21535001. The reversal of 21534991 is 19943512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21534991 - 2³ = 21534983 is a prime.

It is a super-3 number, since 3×21534991³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21534911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767495 + 10767496.

It is an arithmetic number, because the mean of its divisors is an integer number (10767496).

Almost surely, 2^21534991 is an apocalyptic number.

21534991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21534991 is an equidigital number, since it uses as much as digits as its factorization.

21534991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9720, while the sum is 34.

The square root of 21534991 is about 4640.5808903628. The cubic root of 21534991 is about 278.2156556891.

The spelling of 21534991 in words is "twenty-one million, five hundred thirty-four thousand, nine hundred ninety-one".