51620721 has 8 divisors (see below), whose sum is σ = 72876384. Its totient is φ = 32389440.

The previous prime is 51620669. The next prime is 51620729. The reversal of 51620721 is 12702615.

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

It is not a de Polignac number, because 51620721 - 2⁷ = 51620593 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 51620691 and 51620700.

It is not an unprimeable number, because it can be changed into a prime (51620729) 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, 506035 + ... + 506136.

It is an arithmetic number, because the mean of its divisors is an integer number (9109548).

Almost surely, 2^51620721 is an apocalyptic number.

51620721 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

It is an amenable number.

51620721 is a deficient number, since it is larger than the sum of its proper divisors (21255663).

51620721 is a wasteful number, since it uses less digits than its factorization.

51620721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1012191.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 51620721 is about 7184.7561545261. The cubic root of 51620721 is about 372.3414240270.

The spelling of 51620721 in words is "fifty-one million, six hundred twenty thousand, seven hundred twenty-one".