21155671 has 8 divisors (see below), whose sum is σ = 21903488. Its totient is φ = 20412000.

The previous prime is 21155669. The next prime is 21155681. The reversal of 21155671 is 17655112.

21155671 = T₃₇₅₄ + T₃₇₅₅ + T₃₇₅₆.

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

It is a cyclic number.

It is not a de Polignac number, because 21155671 - 2¹ = 21155669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12241 + ... + 13861.

It is an arithmetic number, because the mean of its divisors is an integer number (2737936).

Almost surely, 2^21155671 is an apocalyptic number.

21155671 is the 3756-th centered triangular number.

21155671 is a deficient number, since it is larger than the sum of its proper divisors (747817).

21155671 is a wasteful number, since it uses less digits than its factorization.

21155671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2073.

The product of its digits is 2100, while the sum is 28.

The square root of 21155671 is about 4599.5294324528. The cubic root of 21155671 is about 276.5724614348.

The spelling of 21155671 in words is "twenty-one million, one hundred fifty-five thousand, six hundred seventy-one".