21387151 has 2 divisors, whose sum is σ = 21387152. Its totient is φ = 21387150.

The previous prime is 21387109. The next prime is 21387161. The reversal of 21387151 is 15178312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21387151 - 2⁹ = 21386639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21387101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693575 + 10693576.

It is an arithmetic number, because the mean of its divisors is an integer number (10693576).

Almost surely, 2^21387151 is an apocalyptic number.

21387151 is a deficient number, since it is larger than the sum of its proper divisors (1).

21387151 is an equidigital number, since it uses as much as digits as its factorization.

21387151 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 28.

The square root of 21387151 is about 4624.6244171824. The cubic root of 21387151 is about 277.5775331874.

The spelling of 21387151 in words is "twenty-one million, three hundred eighty-seven thousand, one hundred fifty-one".