21872749 has 2 divisors, whose sum is σ = 21872750. Its totient is φ = 21872748.

The previous prime is 21872737. The next prime is 21872777. The reversal of 21872749 is 94727812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20475625 + 1397124 = 4525^2 + 1182^2 .

It is a cyclic number.

It is not a de Polignac number, because 21872749 - 2⁹ = 21872237 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21872779) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936374 + 10936375.

It is an arithmetic number, because the mean of its divisors is an integer number (10936375).

Almost surely, 2^21872749 is an apocalyptic number.

It is an amenable number.

21872749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21872749 is an equidigital number, since it uses as much as digits as its factorization.

21872749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56448, while the sum is 40.

The square root of 21872749 is about 4676.8310852542. The cubic root of 21872749 is about 279.6626421672.

The spelling of 21872749 in words is "twenty-one million, eight hundred seventy-two thousand, seven hundred forty-nine".