21655051 has 4 divisors (see below), whose sum is σ = 23623704. Its totient is φ = 19686400.

The previous prime is 21655043. The next prime is 21655063. The reversal of 21655051 is 15055612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21655051 - 2³ = 21655043 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21655001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 984310 + ... + 984331.

It is an arithmetic number, because the mean of its divisors is an integer number (5905926).

Almost surely, 2^21655051 is an apocalyptic number.

21655051 is a deficient number, since it is larger than the sum of its proper divisors (1968653).

21655051 is a wasteful number, since it uses less digits than its factorization.

21655051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1968652.

The product of its (nonzero) digits is 1500, while the sum is 25.

The square root of 21655051 is about 4653.4987912322. The cubic root of 21655051 is about 278.7317256951.

The spelling of 21655051 in words is "twenty-one million, six hundred fifty-five thousand, fifty-one".