21387495 has 16 divisors (see below), whose sum is σ = 34282080. Its totient is φ = 11385984.

The previous prime is 21387473. The next prime is 21387497. The reversal of 21387495 is 59478312.

It is not a de Polignac number, because 21387495 - 2⁵ = 21387463 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387497) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11061 + ... + 12849.

It is an arithmetic number, because the mean of its divisors is an integer number (2142630).

Almost surely, 2^21387495 is an apocalyptic number.

21387495 is a deficient number, since it is larger than the sum of its proper divisors (12894585).

21387495 is a wasteful number, since it uses less digits than its factorization.

21387495 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2594.

The product of its digits is 60480, while the sum is 39.

The square root of 21387495 is about 4624.6616092423. The cubic root of 21387495 is about 277.5790214044.

Adding to 21387495 its product of digits (60480), we get a triangular number (21447975 = T₆₅₄₉).

The spelling of 21387495 in words is "twenty-one million, three hundred eighty-seven thousand, four hundred ninety-five".