21423787 has 16 divisors (see below), whose sum is σ = 27873792. Its totient is φ = 15966720.

The previous prime is 21423781. The next prime is 21423793. The reversal of 21423787 is 78732412.

It is an interprime number because it is at equal distance from previous prime (21423781) and next prime (21423793).

It is not a de Polignac number, because 21423787 - 2¹⁹ = 20899499 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21423781) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4278 + ... + 7819.

It is an arithmetic number, because the mean of its divisors is an integer number (1742112).

Almost surely, 2^21423787 is an apocalyptic number.

21423787 is a deficient number, since it is larger than the sum of its proper divisors (6450005).

21423787 is a wasteful number, since it uses less digits than its factorization.

21423787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12138.

The product of its digits is 18816, while the sum is 34.

The square root of 21423787 is about 4628.5836926645. The cubic root of 21423787 is about 277.7359387237.

It can be divided in two parts, 2142 and 3787, that added together give a square (5929 = 77²).

The spelling of 21423787 in words is "twenty-one million, four hundred twenty-three thousand, seven hundred eighty-seven".