21098639 has 2 divisors, whose sum is σ = 21098640. Its totient is φ = 21098638.

The previous prime is 21098633. The next prime is 21098647. The reversal of 21098639 is 93689012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21098639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21098633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10549319 + 10549320.

It is an arithmetic number, because the mean of its divisors is an integer number (10549320).

Almost surely, 2^21098639 is an apocalyptic number.

21098639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21098639 is an equidigital number, since it uses as much as digits as its factorization.

21098639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21098639 is about 4593.3254837862. The cubic root of 21098639 is about 276.3237073920.

The spelling of 21098639 in words is "twenty-one million, ninety-eight thousand, six hundred thirty-nine".