21151660 has 24 divisors (see below), whose sum is σ = 44671536. Its totient is φ = 8412480.

The previous prime is 21151639. The next prime is 21151661. The reversal of 21151660 is 6615112.

It is not an unprimeable number, because it can be changed into a prime (21151661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 699 + ... + 6541.

It is an arithmetic number, because the mean of its divisors is an integer number (1861314).

Almost surely, 2^21151660 is an apocalyptic number.

21151660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21151660 is an abundant number, since it is smaller than the sum of its proper divisors (23519876).

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

21151660 is a wasteful number, since it uses less digits than its factorization.

21151660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6033 (or 6031 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 21151660 is about 4599.0933889192. The cubic root of 21151660 is about 276.5549814526.

Adding to 21151660 its reverse (6615112), we get a palindrome (27766772).

The spelling of 21151660 in words is "twenty-one million, one hundred fifty-one thousand, six hundred sixty".