21564733 has 2 divisors, whose sum is σ = 21564734. Its totient is φ = 21564732.

The previous prime is 21564713. The next prime is 21564743. The reversal of 21564733 is 33746512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18335524 + 3229209 = 4282^2 + 1797^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21564733 is a prime.

It is a super-2 number, since 2×21564733² = 930075418722578, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21564695 and 21564704.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21564703) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10782366 + 10782367.

It is an arithmetic number, because the mean of its divisors is an integer number (10782367).

Almost surely, 2^21564733 is an apocalyptic number.

It is an amenable number.

21564733 is a deficient number, since it is larger than the sum of its proper divisors (1).

21564733 is an equidigital number, since it uses as much as digits as its factorization.

21564733 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15120, while the sum is 31.

The square root of 21564733 is about 4643.7843403845. The cubic root of 21564733 is about 278.3436780869.

It can be divided in two parts, 2156 and 4733, that added together give a square (6889 = 83²).

The spelling of 21564733 in words is "twenty-one million, five hundred sixty-four thousand, seven hundred thirty-three".