21749617 has 2 divisors, whose sum is σ = 21749618. Its totient is φ = 21749616.

The previous prime is 21749603. The next prime is 21749621. The reversal of 21749617 is 71694712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14561856 + 7187761 = 3816^2 + 2681^2 .

It is a cyclic number.

It is not a de Polignac number, because 21749617 - 2¹¹ = 21747569 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21749657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10874808 + 10874809.

It is an arithmetic number, because the mean of its divisors is an integer number (10874809).

Almost surely, 2^21749617 is an apocalyptic number.

It is an amenable number.

21749617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21749617 is an equidigital number, since it uses as much as digits as its factorization.

21749617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21168, while the sum is 37.

The square root of 21749617 is about 4663.6484644536. The cubic root of 21749617 is about 279.1368701051.

It can be divided in two parts, 21749 and 617, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21749617 in words is "twenty-one million, seven hundred forty-nine thousand, six hundred seventeen".