21159651 has 4 divisors (see below), whose sum is σ = 28212872. Its totient is φ = 14106432.

The previous prime is 21159643. The next prime is 21159653. The reversal of 21159651 is 15695112.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21159651 - 2³ = 21159643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21159653) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3526606 + ... + 3526611.

It is an arithmetic number, because the mean of its divisors is an integer number (7053218).

Almost surely, 2^21159651 is an apocalyptic number.

21159651 is a deficient number, since it is larger than the sum of its proper divisors (7053221).

21159651 is an equidigital number, since it uses as much as digits as its factorization.

21159651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7053220.

The product of its digits is 2700, while the sum is 30.

The square root of 21159651 is about 4599.9620650610. The cubic root of 21159651 is about 276.5898041350.

The spelling of 21159651 in words is "twenty-one million, one hundred fifty-nine thousand, six hundred fifty-one".