21501651 has 16 divisors (see below), whose sum is σ = 30543264. Its totient is φ = 13407744.

The previous prime is 21501647. The next prime is 21501653. The reversal of 21501651 is 15610512.

It is not a de Polignac number, because 21501651 - 2² = 21501647 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21501653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7605 + ... + 10041.

It is an arithmetic number, because the mean of its divisors is an integer number (1908954).

Almost surely, 2^21501651 is an apocalyptic number.

21501651 is a deficient number, since it is larger than the sum of its proper divisors (9041613).

21501651 is a wasteful number, since it uses less digits than its factorization.

21501651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2630.

The product of its (nonzero) digits is 300, while the sum is 21.

The square root of 21501651 is about 4636.9872762387. The cubic root of 21501651 is about 278.0720057428.

The spelling of 21501651 in words is "twenty-one million, five hundred one thousand, six hundred fifty-one".