21638151 has 16 divisors (see below), whose sum is σ = 32663520. Its totient is φ = 14152320.

The previous prime is 21638143. The next prime is 21638153. The reversal of 21638151 is 15183612.

21638151 is a `hidden beast` number, since 21 + 638 + 1 + 5 + 1 = 666.

It is not a de Polignac number, because 21638151 - 2³ = 21638143 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21638153) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6130 + ... + 8991.

It is an arithmetic number, because the mean of its divisors is an integer number (2041470).

Almost surely, 2^21638151 is an apocalyptic number.

21638151 is a deficient number, since it is larger than the sum of its proper divisors (11025369).

21638151 is a wasteful number, since it uses less digits than its factorization.

21638151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15183 (or 15177 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 21638151 is about 4651.6825988023. The cubic root of 21638151 is about 278.6591977030.

The spelling of 21638151 in words is "twenty-one million, six hundred thirty-eight thousand, one hundred fifty-one".