21151639 has 2 divisors, whose sum is σ = 21151640. Its totient is φ = 21151638.

The previous prime is 21151619. The next prime is 21151661. The reversal of 21151639 is 93615112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21151639 - 2⁵ = 21151607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21151609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10575819 + 10575820.

It is an arithmetic number, because the mean of its divisors is an integer number (10575820).

Almost surely, 2^21151639 is an apocalyptic number.

21151639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21151639 is an equidigital number, since it uses as much as digits as its factorization.

21151639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1620, while the sum is 28.

The square root of 21151639 is about 4599.0911058599. The cubic root of 21151639 is about 276.5548899286.

The spelling of 21151639 in words is "twenty-one million, one hundred fifty-one thousand, six hundred thirty-nine".