21251451646 has 8 divisors (see below), whose sum is σ = 32738722920. Its totient is φ = 10338544008.

The previous prime is 21251451629. The next prime is 21251451659. The reversal of 21251451646 is 64615415212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21251451646² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143590816 + ... + 143590963.

It is an arithmetic number, because the mean of its divisors is an integer number (4092340365).

Almost surely, 2^21251451646 is an apocalyptic number.

21251451646 is a deficient number, since it is larger than the sum of its proper divisors (11487271274).

21251451646 is a wasteful number, since it uses less digits than its factorization.

21251451646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287181818.

The product of its digits is 57600, while the sum is 37.

Adding to 21251451646 its reverse (64615415212), we get a palindrome (85866866858).

The spelling of 21251451646 in words is "twenty-one billion, two hundred fifty-one million, four hundred fifty-one thousand, six hundred forty-six".