20921251 has 16 divisors (see below), whose sum is σ = 23313024. Its totient is φ = 18653184.

The previous prime is 20921227. The next prime is 20921269. The reversal of 20921251 is 15212902.

It is a cyclic number.

It is not a de Polignac number, because 20921251 - 2¹³ = 20913059 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20921221) 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, 59091 + ... + 59443.

It is an arithmetic number, because the mean of its divisors is an integer number (1457064).

Almost surely, 2^20921251 is an apocalyptic number.

20921251 is a deficient number, since it is larger than the sum of its proper divisors (2391773).

20921251 is a wasteful number, since it uses less digits than its factorization.

20921251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 510.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 20921251 is about 4573.9754043939. The cubic root of 20921251 is about 275.5471245241.

The spelling of 20921251 in words is "twenty million, nine hundred twenty-one thousand, two hundred fifty-one".