21399742 has 32 divisors (see below), whose sum is σ = 39739392. Its totient is φ = 8416224.

The previous prime is 21399739. The next prime is 21399743. The reversal of 21399742 is 24799312.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21399743) 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, 55683 + ... + 56065.

It is an arithmetic number, because the mean of its divisors is an integer number (1241856).

Almost surely, 2^21399742 is an apocalyptic number.

21399742 is a deficient number, since it is larger than the sum of its proper divisors (18339650).

21399742 is a wasteful number, since it uses less digits than its factorization.

21399742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 712.

The product of its digits is 27216, while the sum is 37.

The square root of 21399742 is about 4625.9855166224. The cubic root of 21399742 is about 277.6319941282.

It can be divided in two parts, 2139 and 9742, that added together give a square (11881 = 109²).

The spelling of 21399742 in words is "twenty-one million, three hundred ninety-nine thousand, seven hundred forty-two".