21612156 has 12 divisors (see below), whose sum is σ = 50428392. Its totient is φ = 7204048.

The previous prime is 21612133. The next prime is 21612179. The reversal of 21612156 is 65121612.

It is an interprime number because it is at equal distance from previous prime (21612133) and next prime (21612179).

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-3 number, since 3×21612156³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 900495 + ... + 900518.

It is an arithmetic number, because the mean of its divisors is an integer number (4202366).

Almost surely, 2^21612156 is an apocalyptic number.

It is an amenable number.

21612156 is an abundant number, since it is smaller than the sum of its proper divisors (28816236).

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

21612156 is a wasteful number, since it uses less digits than its factorization.

21612156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1801020 (or 1801018 counting only the distinct ones).

The product of its digits is 720, while the sum is 24.

The square root of 21612156 is about 4648.8876088802. The cubic root of 21612156 is about 278.5475638803.

Adding to 21612156 its reverse (65121612), we get a palindrome (86733768).

The spelling of 21612156 in words is "twenty-one million, six hundred twelve thousand, one hundred fifty-six".