21396551 has 12 divisors (see below), whose sum is σ = 23774016. Its totient is φ = 19240320.

The previous prime is 21396533. The next prime is 21396569. The reversal of 21396551 is 15569312.

It is an interprime number because it is at equal distance from previous prime (21396533) and next prime (21396569).

It is not a de Polignac number, because 21396551 - 2¹⁰ = 21395527 is a prime.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21396511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10826 + ... + 12648.

It is an arithmetic number, because the mean of its divisors is an integer number (1981168).

Almost surely, 2^21396551 is an apocalyptic number.

21396551 is a deficient number, since it is larger than the sum of its proper divisors (2377465).

21396551 is a wasteful number, since it uses less digits than its factorization.

21396551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1942 (or 1931 counting only the distinct ones).

The product of its digits is 8100, while the sum is 32.

The square root of 21396551 is about 4625.6406042839. The cubic root of 21396551 is about 277.6181938414.

The spelling of 21396551 in words is "twenty-one million, three hundred ninety-six thousand, five hundred fifty-one".