21187742 has 8 divisors (see below), whose sum is σ = 32164776. Its totient is φ = 10466152.

The previous prime is 21187697. The next prime is 21187753. The reversal of 21187742 is 24778112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21187742² = 897840822117128, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21187699 and 21187708.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63653 + ... + 63984.

It is an arithmetic number, because the mean of its divisors is an integer number (4020597).

Almost surely, 2^21187742 is an apocalyptic number.

21187742 is a deficient number, since it is larger than the sum of its proper divisors (10977034).

21187742 is a wasteful number, since it uses less digits than its factorization.

21187742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127722.

The product of its digits is 6272, while the sum is 32.

The square root of 21187742 is about 4603.0144470770. The cubic root of 21187742 is about 276.7121478108.

The spelling of 21187742 in words is "twenty-one million, one hundred eighty-seven thousand, seven hundred forty-two".