21240156 has 48 divisors (see below), whose sum is σ = 56899584. Its totient is φ = 6040896.

The previous prime is 21240133. The next prime is 21240161. The reversal of 21240156 is 65104212.

It is a super-2 number, since 2×21240156² = 902288453808672, which contains 22 as substring.

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, 24181 + ... + 25043.

It is an arithmetic number, because the mean of its divisors is an integer number (1185408).

Almost surely, 2^21240156 is an apocalyptic number.

It is an amenable number.

21240156 is an abundant number, since it is smaller than the sum of its proper divisors (35659428).

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

21240156 is a wasteful number, since it uses less digits than its factorization.

21240156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1170 (or 1168 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21240156 is about 4608.7043732485. The cubic root of 21240156 is about 276.9401357250.

Adding to 21240156 its reverse (65104212), we get a palindrome (86344368).

The spelling of 21240156 in words is "twenty-one million, two hundred forty thousand, one hundred fifty-six".