21737987 has 2 divisors, whose sum is σ = 21737988. Its totient is φ = 21737986.

The previous prime is 21737977. The next prime is 21738001. The reversal of 21737987 is 78973712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21737987 - 2⁴ = 21737971 is a prime.

It is not a weakly prime, because it can be changed into another prime (21737977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10868993 + 10868994.

It is an arithmetic number, because the mean of its divisors is an integer number (10868994).

Almost surely, 2^21737987 is an apocalyptic number.

21737987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21737987 is an equidigital number, since it uses as much as digits as its factorization.

21737987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 148176, while the sum is 44.

The square root of 21737987 is about 4662.4014198694. The cubic root of 21737987 is about 279.0871076870.

The spelling of 21737987 in words is "twenty-one million, seven hundred thirty-seven thousand, nine hundred eighty-seven".