21742140 has 48 divisors (see below), whose sum is σ = 69576192. Its totient is φ = 4969536.

The previous prime is 21742139. The next prime is 21742151. The reversal of 21742140 is 4124712.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25464 + ... + 26303.

It is an arithmetic number, because the mean of its divisors is an integer number (1449504).

Almost surely, 2^21742140 is an apocalyptic number.

21742140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21742140 is an abundant number, since it is smaller than the sum of its proper divisors (47834052).

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

21742140 is a wasteful number, since it uses less digits than its factorization.

21742140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51786 (or 51784 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21742140 is about 4662.8467699464. The cubic root of 21742140 is about 279.1048795711.

Adding to 21742140 its reverse (4124712), we get a palindrome (25866852).

The spelling of 21742140 in words is "twenty-one million, seven hundred forty-two thousand, one hundred forty".