21680156 has 6 divisors (see below), whose sum is σ = 37940280. Its totient is φ = 10840076.

The previous prime is 21680149. The next prime is 21680167. The reversal of 21680156 is 65108612.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2710016 + ... + 2710023.

It is an arithmetic number, because the mean of its divisors is an integer number (6323380).

Almost surely, 2^21680156 is an apocalyptic number.

It is an amenable number.

21680156 is a deficient number, since it is larger than the sum of its proper divisors (16260124).

21680156 is a wasteful number, since it uses less digits than its factorization.

21680156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5420043 (or 5420041 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 21680156 is about 4656.1954426334. The cubic root of 21680156 is about 278.8393966120.

Adding to 21680156 its reverse (65108612), we get a palindrome (86788768).

The spelling of 21680156 in words is "twenty-one million, six hundred eighty thousand, one hundred fifty-six".