21506742 has 16 divisors (see below), whose sum is σ = 47792880. Its totient is φ = 7168896.

The previous prime is 21506729. The next prime is 21506753. The reversal of 21506742 is 24760512.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 199083 + ... + 199190.

It is an arithmetic number, because the mean of its divisors is an integer number (2987055).

Almost surely, 2^21506742 is an apocalyptic number.

21506742 is an abundant number, since it is smaller than the sum of its proper divisors (26286138).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21506742 is a wasteful number, since it uses less digits than its factorization.

21506742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398284 (or 398278 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21506742 is about 4637.5361993196. The cubic root of 21506742 is about 278.0939506137.

The spelling of 21506742 in words is "twenty-one million, five hundred six thousand, seven hundred forty-two".