21053987 has 2 divisors, whose sum is σ = 21053988. Its totient is φ = 21053986.

The previous prime is 21053983. The next prime is 21054017. The reversal of 21053987 is 78935012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21053987 - 2² = 21053983 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21053983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10526993 + 10526994.

It is an arithmetic number, because the mean of its divisors is an integer number (10526994).

Almost surely, 2^21053987 is an apocalyptic number.

21053987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21053987 is an equidigital number, since it uses as much as digits as its factorization.

21053987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21053987 is about 4588.4623786188. The cubic root of 21053987 is about 276.1286376130.

Adding to 21053987 its reverse (78935012), we get a palindrome (99988999).

The spelling of 21053987 in words is "twenty-one million, fifty-three thousand, nine hundred eighty-seven".