21740387 has 2 divisors, whose sum is σ = 21740388. Its totient is φ = 21740386.

The previous prime is 21740371. The next prime is 21740417. The reversal of 21740387 is 78304712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21740387 - 2⁴ = 21740371 is a prime.

It is not a weakly prime, because it can be changed into another prime (21740317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10870193 + 10870194.

It is an arithmetic number, because the mean of its divisors is an integer number (10870194).

Almost surely, 2^21740387 is an apocalyptic number.

21740387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21740387 is an equidigital number, since it uses as much as digits as its factorization.

21740387 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9408, while the sum is 32.

The square root of 21740387 is about 4662.6587908617. The cubic root of 21740387 is about 279.0973782548.

It can be divided in two parts, 217 and 40387, that added together give a palindrome (40604).

The spelling of 21740387 in words is "twenty-one million, seven hundred forty thousand, three hundred eighty-seven".