21998749 has 2 divisors, whose sum is σ = 21998750. Its totient is φ = 21998748.

The previous prime is 21998723. The next prime is 21998761. The reversal of 21998749 is 94789912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21483225 + 515524 = 4635^2 + 718^2 .

It is a cyclic number.

It is not a de Polignac number, because 21998749 - 2⁷ = 21998621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21998149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10999374 + 10999375.

It is an arithmetic number, because the mean of its divisors is an integer number (10999375).

Almost surely, 2^21998749 is an apocalyptic number.

It is an amenable number.

21998749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21998749 is an equidigital number, since it uses as much as digits as its factorization.

21998749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 49.

The square root of 21998749 is about 4690.2824008795. The cubic root of 21998749 is about 280.1986218267.

The spelling of 21998749 in words is "twenty-one million, nine hundred ninety-eight thousand, seven hundred forty-nine".